What this calculator does
Turn ounces into grams, or grams back into ounces, exactly. The ounce and the gram are the small-weight units of their systems. The gram, one thousandth of a kilogram, measures everything from flour in a European recipe to the net weight printed on a snack bag. The ounce is the US customary unit for the same jobs: deli meat, letters at the post office, a bar of chocolate or a portion of steak. Anyone following a recipe written in the other system needs this conversion.
An ounce is one sixteenth of the international pound, which makes it exactly 28.349523125 grams. Because that number ends rather than repeating forever, ounces to grams is an exact multiplication. Going from grams back to ounces means dividing by the same number. Type a value, choose the direction, and the working shows the factor used.
Where it's used
Why this math matters outside the classroom:
- Baking. Bakers weigh 8 oz of chocolate as about 227 g on a kitchen scale.
- Letters. Postal clerks weighing mail know a 1 oz letter is about 28.35 g.
- Coffee bags. A 12 oz bag of coffee holds about 340 g.
- Portion sizes. Home cooks portioning meat on a metric scale weigh 4 oz as about 113 g.
- Small parcels. A 3.5 oz package is about 99 g, just under 100 g.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the amount, for example 8 oz or 250 g. Fractions of an ounce can be entered as decimals: ¼ oz is 0.25.
- Pick ounces to grams or grams to ounces.
- Read the result and use the table below it for other common kitchen and postal amounts.
What the inputs mean
- Value to convert
- A weight in avoirdupois ounces (the everyday ounce used for food and mail) for oz → g, or in grams for g → oz.
- Direction
- The conversion direction. The reference table below follows it.
Formula and method
g = oz × 28.349523125 oz = g ÷ 28.349523125 ≈ g × 0.0352739619
Here g is the weight in grams and oz the weight in ounces. The ounce has no definition of its own: it is 1/16 of a pound, and the pound is exactly 453.59237 g. Dividing 453.59237 by 16 gives 28.349523125 g with no rounding at all.
In the other direction, the factor 1 ÷ 28.349523125 is a decimal that never ends, about 0.0352739619 oz per gram. The calculator divides by the exact figure instead of multiplying by a rounded one.
Worked example
A recipe calls for 8 oz of cheese. How many grams is that?
- Start from the exact size of one ounce: 1 oz = 28.349523125 g.
- Multiply by 8, because you have 8 ounces: 8 × 28.349523125 = 226.796185.
Result: 8 oz is 226.796185 g, so about 227 g on a kitchen scale. That is also exactly half a pound.
Understanding the result
Quick estimate: multiply ounces by 28. That lands about 1.2% low, so 8 oz becomes 224 g instead of 226.8 g. No recipe will notice the difference. Rounding up to 30 is easier but runs nearly 6% high. For grams to ounces, divide by 28: 100 g is about 3.6 oz by the shortcut and 3.53 oz exactly.
Handy amounts to remember: 100 g ≈ 3.53 oz; 250 g ≈ 8.82 oz; a 454 g pack is about 16.01 oz, a rounded pound; 1 kg ≈ 35.27 oz.
The biggest trap is the fluid ounce. A fluid ounce measures volume (about 29.57 mL in the US), not weight. One fluid ounce of water happens to weigh close to one ounce, but a fluid ounce of honey or oil does not. If a recipe lists cups or fluid ounces, convert by volume or use an ingredient-density tool.
Assumptions and limitations
- The ounce is the avoirdupois ounce: 1/16 of the international pound.
- Troy ounces, used to price gold and silver, are about 31.10 g. That is roughly 9.7% heavier than the ounce used here.
- Volume measures such as fluid ounces and cups are not handled on this page.
Frequently asked questions
How many grams are in an ounce?
Exactly 28.349523125 g. Most labels and recipes round it to 28 g or 28.35 g.
Is a gold ounce the same as a food ounce?
No. Precious metals are weighed in troy ounces of 31.1034768 g each. Using this converter for a gold price would undervalue the metal by close to a tenth.
Why does a nutrition label say 1 oz (28 g)?
Labels round the gram figure to a whole number for readability. The exact equivalent is 28.35 g, so the rounding hides about a third of a gram per ounce.
Can I convert grams of flour to ounces of flour here?
Yes, as long as both amounts are weights. Grams to ounces works for any ingredient because both are mass units. It is only cups or fluid ounces that need the ingredient's density.
How this calculator is checked
Method: 1 oz = 1/16 lb and 1 lb = 0.45359237 kg exactly (1959 international agreement), so 1 oz = 28.349523125 g. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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