Short answer
- There are 28.35 grams in one everyday ounce, and the exact value is 28.349523125 grams. That is the answer for food, cooking, groceries, parcels, body weight, and almost every other ordinary use of the word ounce in the United States. If a recipe, a label, or a scale says oz with no other qualifier, this is the ounce it means. The longer name for this unit is the avoirdupois ounce. It is one sixteenth of an avoirdupois pound. Because the pound is defined as exactly 453.59237 grams, dividing that figure by 16 gives the ounce exactly: 453.59237 divided by 16 equals 28.349523125 grams. The figure is not an estimate and it does not need to be measured again. It follows directly from the definition of the pound. Two other units share the name and need different handling. A troy ounce, used for gold, silver, platinum, and other precious metals, is 31.1034768 grams, which is heavier than the everyday ounce. A fluid ounce is not a weight at all. It measures volume, so it cannot be converted to grams unless you also know what substance is being measured and how dense that substance is. For most daily tasks, remembering 28.35 grams per ounce is enough. The rest of this article shows how to use that figure accurately for larger and smaller amounts, how to convert grams back to ounces, how much rounding changes a result, and how to check which ounce a listing is really using before you convert it.
By Emma Hudson
Introduction
If a recipe, a food label, a parcel scale, or a product listing gives a weight in ounces and your scale shows grams, you need one number and a clear sense of when that number does not apply. This guide gives the everyday answer first, then the full tables in both directions, worked examples you can follow line by line, and the two exceptions that cause most mistakes: the troy ounce used for precious metals and the fluid ounce, which measures volume rather than weight.
Why the Conversion Is Exact
Many conversions between customary and metric units feel approximate because people usually quote them rounded. This one starts from an exact definition. Under the international yard and pound agreement of 1959, the avoirdupois pound was defined as exactly 0.45359237 kilograms. A kilogram is exactly 1,000 grams, so one pound is exactly 453.59237 grams. An avoirdupois ounce is one sixteenth of a pound by definition, so the gram value of the ounce is a piece of exact arithmetic rather than a laboratory measurement that might shift with a better instrument.
That means every table in this article, and every correct converter elsewhere, is built from the same single factor. If two sources give slightly different answers, at least one has rounded early, used the troy ounce by mistake, or made an arithmetic error. It is never because the true value is uncertain. You can also work in either direction with the same number: multiply ounces by 28.349523125 to get grams, and divide grams by the same number to get ounces.
Grams belong to the metric system, where each step is a power of ten: 1,000 milligrams make one gram, and 1,000 grams make one kilogram. That is why metric amounts often come in round numbers such as 50, 100, 250, and 500 grams, while ounce amounts often come in quarters and halves of a pound.
The Two Formulas and How to Round Them
The full formulas are simple:
Grams equals ounces multiplied by 28.349523125.
Ounces equals grams divided by 28.349523125.
In symbols, g equals oz multiplied by 28.349523125, and oz equals g divided by 28.349523125.
For everyday use, the shortened factor 28.35 is close enough for almost every task. The difference between 28.35 and the exact factor is 0.000476875 grams per ounce, which is less than one thousandth of a gram per ounce. No kitchen scale, bathroom scale, or ordinary parcel scale can display a difference that small. Even at 16 ounces, using 28.35 instead of the exact factor changes the result by less than one hundredth of a gram: 16 multiplied by 28.35 is 453.60 grams, while the exact answer is 453.59237 grams.
Rounding in the other direction needs a little more care, because small gram amounts produce small ounce amounts where rounding is more visible. One gram is 0.0352739619 ounces, usually shown as 0.035 ounces or 0.04 ounces depending on the precision needed. Ten grams is 0.35 ounces to two decimal places. Those rounded figures are fine for cooking and for general comparison, but for a long list of ingredients, convert each amount with the full factor first and round only at the end. Rounding every small item first and then adding the rounded figures can push a total noticeably away from the true total.
A sensible rounding rule is this. For cooking and parcels, give grams to the nearest whole gram or to one decimal place, and give ounces to two decimal places. For precious metals, do not use the everyday ounce at all, as explained below, and follow the precision used in the listing you are reading. For science and calibration work, keep the full factor throughout and state how the final figure was rounded.
Worked Examples From Ounces to Grams
Each example below is recomputed from the exact factor, with the rounding shown separately so you can see where each displayed figure comes from.
One ounce: 1 multiplied by 28.349523125 equals 28.349523125 grams, rounded to 28.35 grams. This is the figure to remember.
Two ounces: 2 multiplied by 28.349523125 equals 56.69904625 grams, rounded to 56.70 grams.
Four ounces to grams is one of the most searched forms of this question, because 4 ounces is a quarter of a pound and a common recipe amount. The calculation is 4 multiplied by 28.349523125, which equals 113.3980925 grams, rounded to 113.40 grams. A US recipe calling for 4 ounces of chocolate, cheese, or butter therefore needs about 113 grams.
Half an ounce: 0.5 multiplied by 28.349523125 equals 14.1747615625 grams, rounded to 14.17 grams. This amount appears often for yeast, spices, gelatin, and small portions of grated cheese or nuts, where a half ounce sounds small but still changes a recipe if it is guessed.
Seven and a half ounces: 7.5 multiplied by 28.349523125 equals 212.6214234375 grams, rounded to 212.62 grams. Amounts ending in a half ounce are common on canned goods and packaged foods, and the same method applies: multiply the full amount, including the fraction, by the exact factor once, rather than converting the whole ounces and the half ounce separately and adding rounded pieces.
Eight ounces: 8 multiplied by 28.349523125 equals 226.796185 grams, rounded to 226.80 grams. Eight ounces is half a pound, so this result should be exactly half of 453.59237 grams, and it is, which is a useful check on your arithmetic.
Sixteen ounces: 16 multiplied by 28.349523125 equals 453.59237 grams exactly. That must be right, because 16 ounces is one pound and one pound is defined as 453.59237 grams. If a conversion for 16 ounces gives you anything else, the factor or the arithmetic is wrong.
Worked Examples From Grams to Ounces
Reading the conversion in reverse answers the question phrased as grams per ounce and the common need to understand a metric label in ounce terms.
One hundred grams: 100 divided by 28.349523125 equals 3.527396195 ounces, rounded to 3.53 ounces. A useful mental shortcut follows from this: 100 grams is about three and a half ounces.
Two hundred and fifty grams: 250 divided by 28.349523125 equals 8.818490487 ounces, rounded to 8.82 ounces. This is a common flour, pasta, and produce amount in metric recipes.
Five hundred grams: 500 divided by 28.349523125 equals 17.636980975 ounces, rounded to 17.64 ounces. That is a little over one pound and one and two thirds ounces, since one pound is 16 ounces.
One kilogram: 1,000 grams divided by 28.349523125 equals 35.27396195 ounces, rounded to 35.27 ounces. In pounds and ounces, that is 2 pounds and about 3.27 ounces, because 32 ounces make 2 pounds and the remaining 3.27 ounces sit on top. The rounded figure 35.274 ounces per kilogram that many converters quote is this same result rounded to three decimal places.
One hundred and seventy five grams: 175 divided by 28.349523125 equals about 6.17 ounces. This kind of mid range amount appears on imported food packaging, where the metric weight is primary and the ounce equivalent is printed for US shoppers.
Five hundred and sixty seven grams: 567 divided by 28.349523125 equals about 20.00 ounces. That is no coincidence. Twenty ounces multiplied by the exact factor is 566.99 grams, which rounds to 567 grams, so a package marked 567 grams is very likely a 20 ounce package with its weight restated in metric terms. Spotting pairs like this helps you tell whether a metric figure is a native metric amount or a converted customary amount.
Ounces to Grams Conversion Table
The table below uses the exact factor and rounds grams to two decimal places. Pounds are shown alongside because many ounce amounts are easier to picture as fractions of a pound.
| Ounces (oz) | Grams (g) | Pounds (lb) |
|---|---|---|
| 0.25 oz | 7.09 g | 0.015625 lb |
| 0.5 oz | 14.17 g | 0.03125 lb |
| 1 oz | 28.35 g | 0.0625 lb |
| 1.5 oz | 42.52 g | 0.09375 lb |
| 2 oz | 56.70 g | 0.125 lb |
| 3 oz | 85.05 g | 0.1875 lb |
| 4 oz | 113.40 g | 0.25 lb |
| 5 oz | 141.75 g | 0.3125 lb |
| 6 oz | 170.10 g | 0.375 lb |
| 7 oz | 198.45 g | 0.4375 lb |
| 8 oz | 226.80 g | 0.5 lb |
| 9 oz | 255.15 g | 0.5625 lb |
| 10 oz | 283.50 g | 0.625 lb |
| 12 oz | 340.19 g | 0.75 lb |
| 14 oz | 396.89 g | 0.875 lb |
| 16 oz | 453.59 g | 1 lb |
| 20 oz | 566.99 g | 1.25 lb |
| 24 oz | 680.39 g | 1.5 lb |
| 32 oz | 907.18 g | 2 lb |
Note the check built into the table. Every time the ounce amount doubles, the gram amount doubles as well, apart from rounding in the last decimal place. The 2 ounce, 4 ounce, 8 ounce, 16 ounce, and 32 ounce rows follow that pattern exactly, which is a quick way to spot a typing error in any conversion table you use elsewhere.
Grams to Ounces Conversion Table
The reverse table covers the gram amounts that appear most often on metric labels and in metric recipes. Ounce values are rounded to two decimal places.
| Grams (g) | Ounces (oz) |
|---|---|
| 1 g | 0.04 oz |
| 5 g | 0.18 oz |
| 10 g | 0.35 oz |
| 25 g | 0.88 oz |
| 50 g | 1.76 oz |
| 75 g | 2.65 oz |
| 100 g | 3.53 oz |
| 150 g | 5.29 oz |
| 200 g | 7.05 oz |
| 250 g | 8.82 oz |
| 300 g | 10.58 oz |
| 400 g | 14.11 oz |
| 500 g | 17.64 oz |
| 750 g | 26.46 oz |
| 1,000 g | 35.27 oz |
For very small amounts, the two decimal place ounce figure loses relative precision: one gram shown as 0.04 ounces is rounded up from 0.035 ounces. For amounts under about 25 grams, such as spices or yeast, weigh in grams directly where you can.
Which Ounce? Avoirdupois, Troy, and Fluid
Most confusion about grams in an ounce comes from the fact that English uses the word ounce for three different units. They share a name and a history, but they are not interchangeable, and using the wrong one gives a wrong answer even when the arithmetic is perfect.
The avoirdupois ounce: the everyday ounce
The avoirdupois ounce, at 28.349523125 grams, is the everyday ounce covered by most of this article. It is used for food, groceries, body weight, parcels, and general commerce. It contains 437.5 grains, and 16 of these ounces make one avoirdupois pound of 7,000 grains. When no qualifier is given, assume this one. Product labels, recipes, and parcel scales in the United States use it by default.
The troy ounce: precious metals
The troy ounce, at exactly 31.1034768 grams, is used for precious metals such as gold, silver, and platinum, and for gemstones. It contains 480 grains, so it is heavier than the everyday ounce grain for grain as well as gram for gram. The difference is 31.1034768 minus 28.349523125, which equals 2.753953675 grams, or about 2.75 grams. In percentage terms, a troy ounce is about 9.7 percent heavier than an avoirdupois ounce.
That difference is large enough to matter for money. If a price is quoted per troy ounce and you convert it using the everyday figure, you will understate the weight involved by almost a tenth. If you weigh a food item using the troy figure, you will overstate its weight by the same proportion. Bullion, coin, and jewelry listings normally intend troy ounces, and many say so explicitly with the abbreviation oz t or ozt. Where a precious metal listing just says oz, check the context carefully before converting, because in that trade the troy meaning is the working assumption.
A related trap is the troy pound. An avoirdupois pound is 16 avoirdupois ounces and weighs 453.59237 grams. A troy pound is only 12 troy ounces and weighs 373.2417216 grams, which is lighter than the everyday pound even though each troy ounce is heavier than each everyday ounce. The two systems agree on the word pound and disagree on almost everything else. That is why precious metal weights should always be handled in troy ounces directly, rather than converted through pounds, where the wrong kind of pound can quietly enter the calculation.
To put the troy conversion in the same form as the main one: 100 grams of a precious metal is 100 divided by 31.1034768, which equals about 3.22 troy ounces, not the 3.53 everyday ounces that 100 grams equals in food terms. One kilogram is about 32.15 troy ounces, compared with 35.27 everyday ounces.
The fluid ounce: volume, not weight
The fluid ounce is not a weight at all. It is a volume. A US fluid ounce is 29.57353 milliliters when rounded to five decimal places, and the exact US value is 29.5735295625 milliliters. An imperial fluid ounce, used in the British imperial system, is smaller, at about 28.413 milliliters. The US system divides a gallon into 128 fluid ounces, while the imperial system divides its larger gallon into 160 fluid ounces, which is how the two fluid ounces end up different sizes.
A US fluid ounce of water weighs close to 29.57 grams, because one milliliter of water has a mass of about one gram. That near match is a property of water, not a property of the units. A fluid ounce of honey weighs considerably more than a fluid ounce of water, because honey is denser than water, and a fluid ounce of oil weighs less, because oil is less dense than water and floats on it. The volume is the same in each case. Only the density changes, and with it the weight.
The practical rule follows directly. Never convert fluid ounces to grams, or grams to fluid ounces, without knowing which substance is involved. If a recipe gives a liquid in fluid ounces and you want to weigh it, look up the weight for that specific liquid, or simply measure the volume as written. If a recipe gives an ingredient in fluid ounces but the ingredient is a dry solid, treat that as a warning sign in the recipe itself, because a volume measure for a solid depends on how finely it is ground and how firmly it is packed.
On labels, the abbreviation helps. A weight ounce is written oz, and a fluid ounce is written fl oz. Nutrition and drinks labels use fl oz for liquids. If you see fl oz, do not apply the 28.35 gram factor at all.
Practical Uses
Cooking and baking
In the kitchen, the conversion matters most when a recipe from one country meets a scale from another. A US recipe calling for 4 ounces of chocolate needs 113.40 grams. A metric recipe calling for 200 grams of butter needs about 7.05 ounces. Weighing is more accurate than converting through cups, because a cup of an ingredient varies with how it is packed, how fine it is, and how it was spooned or scooped, while a gram is a gram regardless of packing.
If your scale only shows grams and a recipe gives ounces, convert the whole recipe before you start rather than converting spoonful by spoonful as you go. Converting in advance is less error prone, especially when several ingredients are involved and when a recipe is being scaled up or down at the same time. Write the gram figure next to each ounce figure once, check the large items against the tables above, and then cook from the gram list.
Baking rewards the extra care. Flour, sugar, and butter ratios drive texture, and an error of even half an ounce, about 14 grams, in a small batch can change the result. For a stew or a sauce, a similar error is rarely noticeable.
Parcels and postage
Carriers often price by weight bands and round a parcel up to the next band. Convert exactly, then round up as the carrier does. A parcel weighing 100 grams is 3.53 ounces, which a carrier charging by the whole ounce would treat as 4 ounces. A parcel weighing 500 grams is 17.64 ounces, above one pound, so it should not be priced as a one pound parcel. Many shipping disputes turn out to be conversion errors, or a fluid ounce figure treated as a weight, rather than a faulty scale.
Precious metals and jewelry
For precious metals, start by confirming that the unit is the troy ounce, then use 31.1034768 grams per troy ounce in both directions. Grams to troy ounces means dividing by 31.1034768. Troy ounces to grams means multiplying by 31.1034768. Keep the everyday factor out of these calculations entirely. A one troy ounce coin therefore weighs 31.10 grams rounded to two decimal places, not 28.35 grams, and calling it 28.35 grams understates its metal content by about 2.75 grams.
Labels, nutrition, and small items
US food labels commonly give a serving weight in grams with an ounce equivalent, or the reverse. A serving listed as 28 grams is a rounded version of one ounce, and 56 grams is a rounded version of two ounces at 56.70 grams. Differences of a gram or so are usually label rounding, not an error. Ounces and grams are most useful at the small end of the scale: letters, spices, coffee, tea, seeds, and craft materials, where a single ounce is a meaningful share of the whole amount. For body weight, most people track pounds or kilograms, where changes are easier to read.
Common Mistakes and How to Avoid Them
The first common mistake is using 28 grams as the factor. That rough rounding loses 0.349523125 grams per ounce, about a third of a gram. For one ounce in a casual estimate, that may not matter. For 16 ounces, it loses about 5.59 grams, which is visible on a kitchen scale and enough to matter in baking and in postage bands. Use 28.35 grams for anything you actually measure, and save 28 grams for a spoken estimate only.
The second mistake is mixing up the troy and avoirdupois ounces, covered above. The check is to ask what is being weighed. If it is a precious metal or a gemstone and the source is a dealer, a mint, or a market price, expect troy. If it is food, mail, or a household item, expect avoirdupois.
The third mistake is treating a fluid ounce as a weight ounce. The check is the abbreviation and the substance. Fl oz means volume. A weight conversion needs a weight unit and, for liquids being converted from volume, a density for that specific liquid.
The fourth mistake is rounding too early. Convert with the full factor, add or scale in the converted units if needed, and round once at the end. This is especially important when scaling a recipe, where each ingredient is multiplied by the same scaling factor. Scale first in the original unit or convert first with full precision, but do not round, then scale, then round again, because the errors stack.
Other Ways the Question Is Asked
People phrase this question in many ways, and the answer is the same conversion in each case. How many grams in a ounce, how many grams in one oz, and the same wording with a punctuation slip or a duplicated word all ask for grams per ounce, and the answer is 28.35 grams for the everyday avoirdupois ounce, 28.349523125 grams exactly. Oz is simply the abbreviation for ounce, so an oz question and an ounce question are the same question. The reversed form, 4 ounces to grams, is worked in full above and equals 113.40 grams.
One further phrasing deserves a brief, neutral note. Searches also combine this conversion with weighing cannabis. This article gives no instructions or encouragement relating to that use and covers only the unit conversion itself, which is 28.35 grams per everyday ounce regardless of what is being weighed. Readers in places where cannabis is regulated should follow their local law.
Frequently Asked Questions
How many grams are in an ounce?
There are 28.349523125 grams exactly in one everyday avoirdupois ounce, usually rounded to 28.35 grams. This is the ounce used for food, cooking, parcels, and general commerce. If the ounce is a troy ounce for precious metals, the answer is different, at 31.1034768 grams.
How many grams are in a troy ounce?
There are 31.1034768 grams in one troy ounce. Troy ounces are used for precious metals such as gold, silver, and platinum, and for gemstones, not for food. A troy ounce is about 2.75 grams heavier than an everyday ounce, or about 9.7 percent heavier.
How many grams is 4 ounces?
Four ounces is 113.40 grams, from 4 multiplied by 28.349523125, which equals 113.3980925 grams before rounding. Four ounces is a quarter of a pound, so this is also a quarter of 453.59237 grams.
How many ounces is 100 grams?
One hundred grams is 3.53 ounces, from 100 divided by 28.349523125, which equals 3.527396195 ounces before rounding. As a shortcut, 100 grams is about three and a half ounces.
How many grams is half an ounce?
Half an ounce is 14.17 grams, from 0.5 multiplied by 28.349523125, which equals 14.1747615625 grams before rounding.
Is a fluid ounce the same as an ounce in grams?
No. A fluid ounce measures volume, at 29.57353 milliliters for a US fluid ounce, while an ounce in grams measures weight or mass. They come close to each other only for water, because a milliliter of water has a mass of about one gram. For honey, oil, flour, or any other substance, a fluid ounce and a weight ounce give different amounts.
Why do some sources say 28 grams in an ounce?
That is a rough rounding that loses about a third of a gram per ounce, and about 5.59 grams over a full pound. It is acceptable for a very rough spoken estimate, but for anything that is measured, cooked, posted, or sold, use 28.35 grams, or the exact factor 28.349523125 for precise work.
How many ounces are in a kilogram?
One kilogram, which is 1,000 grams, is 35.27 ounces, from 1,000 divided by 28.349523125, which equals 35.27396195 ounces before rounding. In troy ounces, one kilogram is about 32.15 troy ounces, because the troy ounce is heavier.
How many grams per ounce should I use for cooking?
Use 28.35 grams per ounce for cooking. The difference from the exact factor is less than one thousandth of a gram per ounce, which no kitchen scale can display. Convert the whole recipe before you start where you can, and round each ingredient to the nearest whole gram.
Is 28.35 grams exact?
No. 28.35 grams is the exact value rounded to two decimal places. The exact value is 28.349523125 grams, which comes from the definition of the pound as exactly 453.59237 grams divided by 16 ounces per pound. Both figures describe the same ounce. Use the longer figure when precision matters and the shorter one for everyday work.
Keep reading: Kilograms to Ounces
Keep reading: Ounces to Pounds
Keep reading: How Many Grams in a Cup? Why There Is No Single Answer
Sources & references
- National Institute of Standards and Technology, NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement. Used for the avoirdupois system (16 ounces to one pound, 437.5 grains to one avoirdupois ounce, and one avoirdupois ounce equal to 0.028349523125 kilograms, which is 28.349523125 grams), for the troy system (480 grains to one troy ounce, 12 troy ounces to one troy pound, and one troy ounce equal to 31.1034768 grams in the equivalents tables), and for liquid volume (128 US fluid ounces to one gallon and one US fluid ounce equal to 29.57353 milliliters in the equivalents tables, with the British system noted as 160 fluid ounces to one gallon). https://www.nist.gov/document/2026-nist-handbook-44-appendix-c
