Unit converter
Ounces to Grams Converter
Convert ounces to grams with the exact avoirdupois factor used by this calculator: 1 oz = 28.349523125 g. This page is for mass, not fluid ounces, so it fits kitchen scales, recipe ingredients, food packaging, small postal parcels, gym accessories, and luggage items listed by weight. It is useful when an American packet gives ounces but a UK or European recipe, Royal Mail guide, or nutrition label asks for grams. Enter any ounce value and the result follows the fixed 1959 yard-and-pound basis.
1 ounce = 28.3495 grams
Common ounces to grams values
| Ounces | Grams |
|---|---|
| 1 oz | 28.3495 g |
| 2 oz | 56.699 g |
| 5 oz | 141.75 g |
| 10 oz | 283.5 g |
| 20 oz | 566.99 g |
| 50 oz | 1,417.48 g |
| 100 oz | 2,834.95 g |
How to convert
- Start with the weight in avoirdupois ounces, the everyday ounce used with pounds.
- Multiply by the exact factor 28.349523125, because one ounce is exactly 28.349523125 grams.
- The answer is the same mass expressed in grams, ready for a metric scale or label.
- To convert back from grams to ounces, divide the gram value by 28.349523125.
- For a quick mental estimate, use 30 g per ounce and then take off about 5.5 percent: 4 oz is close to 113 g, not 120 g.
grams = ounces * 28.349523125
The mass table defines one ounce as 28.349523125 grams. Multiplying an ounce value by 28.349523125 therefore gives the gram value. The reverse conversion divides by the same fixed factor.
- oz
- the weight in avoirdupois ounces you start with
- 28.349523125
- grams in one avoirdupois ounce, by definition
Worked example
A 12 oz bag of coffee beans is 12 multiplied by 28.349523125, which equals 340.1942775 g. A cafe stock sheet might round that to 340.19 g, while a home recipe would usually treat it as about 340 g.
Key facts
- One avoirdupois ounce is exactly 28.349523125 g.
- Sixteen ounces make one pound, so 16 oz is exactly 453.59237 g.
- Eight ounces is 226.796185 g, a common food-pack and recipe size.
- This conversion is not for troy ounces, which are used for precious metals.
Tips
- When checking food packaging, use the gram result for nutrition per 100 g comparisons.
- For postage or luggage, round up if a carrier charges by weight band.
- Keep the full decimal result until the last step if you are adding several ounce quantities.
Frequently asked questions
How many grams is 1 oz?+
One avoirdupois ounce is exactly 28.349523125 grams.
Is an ounce the same as a fluid ounce?+
No. This calculator converts weight ounces. A fluid ounce measures volume, and US and imperial fluid ounces are different sizes.
Why does 16 oz equal 453.59237 g?+
There are exactly 16 ounces in one avoirdupois pound, and one pound is exactly 453.59237 g, so 16 oz converts to 453.59237 g.
How should I round ounces to grams for cooking?+
For most recipe ingredients, round to the nearest gram. For spices, coffee, supplements, or postage, keep at least one decimal place if the scale supports it.
Things to watch
- Rounding every ounce line separately can create a noticeable difference in a multi-ingredient recipe or parcel manifest.
- US and imperial weight ounces use the same avoirdupois definition here; do not apply this page to US or imperial fluid ounces.
Sources
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement · NIST
- International yard and pound agreement (1959) · NIST
- Weights and Measures Act 1985 · UK legislation.gov.uk
Last updated: 2026-01-01
Conversions use internationally defined factors. Provided for general use; verify critical measurements independently.