Ounces and grams
The avoirdupois ounce is one sixteenth of a pound: exactly 28.349523125 grams. US recipes, food packaging, postage and shipping weights use ounces. It is not the fluid ounce, which measures volume.
The gram is one thousandth of a kilogram. Recipes, nutrition labels, postage and small parcels use grams.
Worked example
Convert 8 oz: 8 × 28.349523125 = 226.796185, so 8 ounces is 226.796185 grams. Likewise 2 oz = 56.69904625 g.
Estimating in your head
Multiply by 28 for a quick figure; it is off by about 1.2%. For 8 oz that gives 224 g, against 226.796 exactly.
Going the other way
To convert grams to ounces, divide by 28.349523125 (or multiply by 0.0352739619496). The swap button between the boxes opens that page.
How this works
g = oz × 28.349523125
1 oz = 0.028349523125 kg and 1 g = 0.001 kg, both by definition, so the factor is their ratio: 28.349523125 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many grams are in a ounce?
1 ounce = 28.349523125 grams, exactly. The value follows from the unit definitions, so it never changes.
How do I convert ounces to grams?
Multiply by 28.349523125. For example, 2 oz × 28.349523125 = 56.69904625 g.
What is 10 oz in grams?
10 oz = 283.4952313 g. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- Federal Register 59-5442 (1959) — Refinement of values for the yard and the pound
- Wikipedia — Avoirdupois system
Reviewed Oct 17, 2026 · test vectors fixtures/units/mass/ounces-to-grams/