Weight in ounces:
Table of Contents
Grams to ounces — instant, exact conversion
Enter any weight in grams and this calculator returns the equivalent in avoirdupois ounces using the internationally defined factor of 28.349523125 g per ounce. Ideal for cooking, postage, nutrition labels, and laboratory work.
The formula
To convert grams to ounces, divide the gram value by the exact conversion factor:
oz = g ÷ 28.349523125
- oz — the result in avoirdupois ounces.
- g — the input weight in grams.
- 28.349523125 — the exact number of grams in one avoirdupois ounce, fixed by the 1959 International Yard and Pound Agreement.
Worked example
Using the calculator’s default input of 100 g:
- Take the gram value: 100 g.
- Divide by 28.349523125: 100 ÷ 28.349523125 = 3.52740...
So 100 g ≈ 3.527 oz. A handy shortcut: 100 g is just over 3½ ounces.
Conversion table
Common gram values converted to avoirdupois ounces:
| Grams (g) | Ounces (oz) |
|---|---|
| 1 | 0.035 |
| 10 | 0.353 |
| 25 | 0.882 |
| 50 | 1.764 |
| 75 | 2.646 |
| 100 | 3.527 |
| 150 | 5.291 |
| 200 | 7.055 |
| 250 | 8.818 |
| 300 | 10.582 |
| 500 | 17.637 |
| 750 | 26.455 |
| 1000 | 35.274 |
History & standards
The gram was introduced in revolutionary France in the 1790s as part of the metric system — originally defined as the mass of one cubic centimetre of pure water at 4°C. Today the gram is derived from the kilogram, which since 2019 is defined by fixing the numerical value of the Planck constant, giving the unit a permanent, artefact-free definition.
The avoirdupois ounce is 1⁄16 of an avoirdupois pound, which has been defined as exactly 0.45359237 kg since the 1959 International Yard and Pound Agreement. One ounce therefore equals exactly 28.349523125 g. There is also a troy ounce (31.1035 g), used only for precious metals; this calculator uses the avoirdupois ounce.
Common applications
- Cooking and baking. US recipes state dry-ingredient weights in ounces; European and UK recipes use grams. Converting lets you follow any recipe precisely.
- Nutrition labels. US labels show serving sizes in both grams and ounces; quickly cross-check or compare products from different countries.
- Postal and shipping. Many carriers price small packages by the ounce, while kitchen scales read in grams.
- Pharmaceuticals & supplements. Active-ingredient quantities are typically listed in grams or milligrams; converting helps when sourcing products from different markets.
- Jewellery (non-precious). Fashion jewellery is sold by avoirdupois weight; only fine metal jewellery uses troy ounces.
Reverse conversion
To convert ounces back to grams, multiply by 28.349523125: g = oz × 28.349523125 — or use our ounces to grams calculator.
Limitations & gotchas
- Avoirdupois vs troy. If you are weighing gold, silver or other precious metals, you need the troy ounce (31.1035 g), not the 28.35 g used here.
- Fluid ounces are different. A US fluid ounce measures volume (about 29.57 mL), not mass. Do not use this calculator for liquid volumes.
- Rounding. The exact factor is 28.349523125 g; using 28.35 introduces an error of about 0.0002% — negligible for cooking but significant for pharmaceutical-grade work.
- Mass vs weight. Strictly speaking, grams and ounces measure mass. “Weight” in everyday language is used loosely to mean mass — acceptable in commerce but technically distinct in physics.
Sources & references
- NIST SP 811 — Guide for the Use of the International System of Units (SI), National Institute of Standards and Technology.
- BIPM — International Bureau of Weights and Measures, The International System of Units (SI), 9th edition (2019).
- 1959 International Yard and Pound Agreement (fixing 1 lb = 0.45359237 kg exactly).
FAQs
One avoirdupois ounce is defined as exactly 28.349523125 grams — often rounded to 28.35 g for everyday use. This exact value has been fixed by international agreement since 1959.
Divide the number of grams by 28.349523125: oz = g ÷ 28.349523125. For quick mental estimates, dividing by 28.35 or multiplying by 0.03527 works well.
Avoirdupois ounces — the standard ounce used for food, groceries, body weight and everyday goods in the US and UK. The troy ounce (31.1035 g) is a separate unit used exclusively for precious metals such as gold and silver. If you are weighing gold or silver, use a troy-ounce conversion.
100 ÷ 28.3495 ≈ 3.527 oz. A quick rule of thumb: 100 g is just over 3½ oz.
The avoirdupois system (from medieval French “avoir de pois” — goods of weight) was used for trade goods; the troy system descends from the Troyes market in France and was adopted for coinage and precious metals. Both survived into modern use because they serve distinct industries. The troy ounce is about 10% heavier than the avoirdupois ounce.
The conversion factor 28.349523125 g/oz is exact by definition — it was fixed by the 1959 International Yard and Pound Agreement. Any rounding error comes only from how many decimal places the calculator displays.