Ounces to grams Converter

How many grams are in a ounce?

One ounce is 28.349523 grams. The full conversion is grams = ounces × 28.349523125, and going the other way you divide instead of multiply.

A few anchor values worth memorising: 28.349523 g to the ounce, 283.495231 g to ten, and 2,834.952313 g to a hundred. The calculator above handles the rest, including the awkward decimals.

The reference table under the converter lists the values people look up most often, so for a common figure you can read the answer off directly rather than typing anything.

Worked examples

Three worked examples, each multiplying by 28.34952313:

2.5 oz × 28.349523 = 70.8738 g. 25 oz × 28.349523 = 708.7381 g. 250 oz × 28.349523 = 7,087.3808 g.

To reverse any of them, divide instead of multiplying — or use the swap button above, which does the same thing without the arithmetic. Reversing a converted value should return you to exactly what you started with; if it does not, something has been rounded too early.

Doing this conversion in your head

The exact factor is 28.34952313, which nobody multiplies by in their head. It is very close to 312/11, so multiplying by 312 and dividing by 11 lands within 0.05% of the correct answer — accurate enough for anything short of engineering work.

Since the factor is greater than one, the number always gets bigger: a ounce is smaller than a gram, so any quantity converts to more of them. If your answer came out smaller, you have divided when you should have multiplied.

That sanity check catches the majority of real conversion errors. Before trusting any converted figure, ask whether the direction of change makes sense — it takes a second and it is the single most effective safeguard there is.

When you need to convert ounces to grams

The need for this conversion almost always comes from a mismatch: a figure measured in one system that has to be reported in another.

On the source side, ounces appear in US recipes, postal rates and packaged food weights. On the target side, grams are recipe quantities, postage weights and laboratory measurements. The conversion is essentially a translation between those two worlds — most often because a figure produced in one context has to be understood, submitted or acted on in the other.

Where the converted figure will be cut, dosed, billed or filed, round once at the end rather than at each step. For a rough sense of scale, round freely.

The tool itself is deliberately trivial: a multiplication running locally, with no account, no tracking and no network request.

What a ounce and a gram actually are

The ounce (oz). One sixteenth of a pound; the avoirdupois ounce used for food and post.

The gram (g). The kitchen and laboratory unit across most of the world.

The two units describe the same physical quantity, mass, from different traditions. Once both were tied to the same defined standard, converting between them became exact arithmetic rather than measurement.

Common mistakes when converting ounces to grams

There are two different ounces. The avoirdupois ounce used for food and post is 28.35 grams; the troy ounce used for precious metals is 31.10 grams, about 10% heavier. A price quoted "per ounce" for gold always means troy. This converter uses the avoirdupois ounce.

If you are converting many values, change the source unit in the dropdown rather than converting through an intermediate unit. Every extra hop is another rounding opportunity.