Grams to Ounces Calculator

Background.

A cookbook from Britain or Europe asks for 340 g of pasta, and your kitchen scale reads in ounces. Divide by 28.349523125 and you get 11.9931 oz, a whisker under twelve. The coincidence runs the other way round: 12 oz is 340.19 g, which is why an American box marked 12 oz so often shows 340 g printed beside it.

The divisor is a definition rather than a measurement. Since 1959 the avoirdupois pound has been fixed at exactly 0.45359237 kilograms, and an ounce is one sixteenth of a pound, so 28.349523125 g carries no uncertainty at all. Britain and the United States share this ounce, so a weight in ounces means the same thing in a recipe from either country.

In everyday use, getting the right ounce matters more than the ninth decimal place. The avoirdupois ounce weighs food, letters and parcels. Gold and silver are priced in troy ounces of 31.1034768 g, about 10% heavier, and the ounces in many liquid recipes are fluid ounces, a measure of volume rather than weight. Convert with this factor only when the ounce you are dealing with is a weight.

What is grams to ounces calculator?

The gram is the metric unit of mass, one thousandth of a kilogram. The avoirdupois ounce is the everyday ounce of the US customary and British imperial systems: one sixteenth of a pound, or 437.5 grains. Linking them is a single exact ratio, 1 oz = 28.349523125 g, so converting grams to ounces means dividing by that number, or equivalently multiplying by about 0.035274.

How to use this calculator.

1. 01Enter the weight in grams, from 0 up to 50,000 g (50 kg).
2. 02Read the result in ounces and round it to whatever your scale can actually show.
3. 03For a large result, divide the ounces by 16 to get pounds: 1,000 g is 35.274 oz, which is 2 lb and 3.274 oz.
4. 04If the ounce you need is a troy ounce for precious metal, or a fluid ounce for a liquid, use a troy or volume conversion instead.

The formula.

The conversion is ounces = grams ÷ 28.349523125. The constant comes straight from the 1959 international definition of the pound: 0.45359237 kg ÷ 16 = 0.028349523125 kg, or 28.349523125 g, exact by definition because both numbers in the division are exact. Its reciprocal, 0.0352739619 oz per gram, gives the same answer by multiplication. Shortcuts drift by predictable amounts: dividing by 28.35 is within 0.0017% of the exact result, dividing by 28 reads about 1.25% high, and multiplying by 0.035 reads about 0.78% low. Results are shown to ten decimal places, and a negative weight is rejected.

A worked example.

Frequently asked questions.

References& sources.

1. [1]National Bureau of Standards (1959). Refinement of Values for the Yard and the Pound — establishes the international avoirdupois pound as exactly 0.45359237 kilograms, from which the ounce (1/16 lb = 28.349523125 g) is derived.
2. [2]National Institute of Standards and Technology (2008). NIST Special Publication 811: Guide for the Use of the International System of Units (SI), Appendix B — Conversion Factors.