Ounces to Grams Calculator - Convert oz to g

About the Ounces to Grams Calculator

American recipes, US product packaging, postage rates and precious-metal prices all use ounces, while kitchen scales, nutrition labels and shops in most of the world weigh in grams. Anyone baking from an American cookbook, comparing jar sizes, posting a letter abroad or checking the weight of a gold coin needs to turn ounces into grams. There is one twist: there are two different ounces. Everyday goods use the avoirdupois ounce, while gold, silver and platinum are weighed in troy ounces, which are nearly ten percent heavier.

This ounces to grams calculator converts either kind of ounce to grams exactly. It also shows kilograms and pounds, a rounded figure for cooking or bullion, and the same weight in the other kind of ounce.

How to Use the Ounces to Grams Calculator

Enter the weight in ounces. Decimals work, such as 3.5 or 0.25.

Choose the type of ounce: everyday (avoirdupois) for food, post and general weights, or troy for precious metals.

The grams appear at once, with kilograms, a rounded value and the other ounce.

The Formula

  everyday ounce:  grams = ounces × 28.349523125
  troy ounce:      grams = ounces × 31.1034768

  1 lb = 16 everyday ounces = 453.59237 g
  1 troy pound = 12 troy ounces = 373.2417216 g

Both factors are exact definitions, so the only rounding is in the displayed result.

Step-by-Step Example

8 ounces of butter.

  8 × 28.349523125 = 226.796 g

So 8 oz is 226.796 grams, half a pound, usually rounded to 225 g in metric recipes. Two standard US sticks of butter weigh 8 oz.

One troy ounce of gold.

  1 × 31.1034768 = 31.1035 g

A 1 oz gold coin contains 31.10 grams of gold, the same as about 1.09714 everyday ounces.

Common Kitchen Weights

  1 oz   = 28.3495 g        6 oz   = 170.097 g
  2 oz   = 56.699 g         8 oz   = 226.796 g
  3 oz   = 85.0486 g        12 oz  = 340.194 g
  4 oz   = 113.398 g        16 oz  = 453.592 g (1 lb)

Many cooks use 25 g or 30 g as a rough ounce. The first is about 12 percent low and the second about 6 percent high. Either is fine for a stew, but for bread, cakes and pastry use the exact figure or round to the nearest 5 g, as the calculator does.

Two Kinds of Ounce

The avoirdupois system, from an old French phrase for "goods of weight", is the everyday system of pounds and ounces, with 16 ounces to the pound. The troy system dates from medieval trading fairs at Troyes in France and survives only for precious metals, with 12 troy ounces to a troy pound. Confusingly, the troy ounce is heavier than the everyday ounce, but the troy pound is lighter than the everyday pound, because it has fewer ounces in it.

Gold, silver, platinum and palladium prices are always quoted per troy ounce. If you convert a bullion weight with the everyday factor, the grams come out almost 10 percent too low.

Fluid Ounces Are Different

Recipes also use fluid ounces, which measure volume, not weight. A US fluid ounce is 29.5735 millilitres and a UK fluid ounce 28.4131 millilitres. For water, a fluid ounce happens to weigh about an ounce, but for flour, sugar or honey the weight of a fluid ounce is quite different, so this calculator should be used only for ounces of weight.

Postage and Parcels

US postal prices step up by the ounce for letters and small packets, while most other countries use grams. A 3 oz letter weighs 85.05 g and a 13 oz packet 368.54 g. When sending mail internationally, convert and round up to be sure the item falls in the right weight band.

Package Sizes and Unit Prices

Supermarket products sold internationally often show both units, but the metric figure is usually the exact one and the ounce figure rounded, or the other way round for American goods. A 16 oz jar holds 453.6 g; a 12 oz can about 340 g; and a 6.5 oz tin about 184 g. When comparing value between brands or countries, convert everything to grams and divide the price by the weight to get a price per 100 g. That makes a metric pack and an imperial pack directly comparable, even when their sizes look unrelated, and it avoids the common mistake of assuming a pack labelled in round ounces is the same as a similar-looking metric pack.

Understanding Your Result

The headline is the weight in grams.

The kilograms line gives the weight in kilograms, and in pounds for everyday ounces.

The rounded line gives the nearest 5 g for cooking, or two decimal places of a gram for troy ounces, as bullion is weighed.

The other ounce line converts the weight into the other kind of ounce.

When Should You Use This Calculator?

Use it to follow American recipes on metric kitchen scales.

Use it to compare package sizes labelled in ounces and grams.

Use it to check the gold or silver content of coins and bars in troy ounces.

Use it for postage weights and nutrition labels.

Common Mistakes

Using fluid ounces as weight. Fluid ounces are volume; this is weight only.

Using everyday ounces for gold. Precious metals use troy ounces of 31.1 g.

Rounding an ounce to 30 g in baking. It adds about 6 percent.

Forgetting 16 ounces make a pound. 20 oz is 1 lb 4 oz, not 2 lb.

Converting a converted figure. Start from the original ounces to avoid double rounding, especially when scaling a recipe up or down.