The ounce (oz) and gram (g) are two of the most commonly encountered weight units worldwide. Ounces dominate in the United States for food packaging, postage, and recipes, while grams are the standard in virtually every other country and in scientific contexts. Whether you're following an American recipe abroad, comparing product weights, or calculating shipping costs, converting ounces to grams is a skill you'll use frequently.
The avoirdupois ounce — the standard ounce used for everyday weights — equals exactly 28.349523125 grams. This definition has been fixed by international agreement since 1959. Note that this is different from the troy ounce (31.1035 g), which is used exclusively for precious metals like gold and silver.
| Ounces (oz) | Grams (g) | Common Use |
|---|---|---|
| 0.25 oz | 7.09 g | Small snack portion |
| 0.5 oz | 14.17 g | Butter pat |
| 1 oz | 28.35 g | Shot of liquid, letter stamp |
| 2 oz | 56.70 g | Standard chocolate bar |
| 3 oz | 85.05 g | Deck of cards (protein serving) |
| 4 oz | 113.40 g | Half cup butter, chicken breast |
| 6 oz | 170.10 g | Steak portion |
| 8 oz | 226.80 g | One cup (volume-to-weight), large steak |
| 12 oz | 340.19 g | Standard soda can, bag of coffee |
| 16 oz | 453.59 g | 1 pound |
| 24 oz | 680.39 g | Large beverage bottle |
| 32 oz | 907.18 g | 2 pounds, quart container |
American recipes use ounces while European, Asian, and Australian recipes use grams. A recipe calling for 8 oz of chocolate chips? That's 226.8 g. Need 4 oz of butter? That's 113.4 g. For baking especially, using a kitchen scale with grams provides far more accuracy than measuring cups, which is why many professional bakers prefer metric.
USPS uses ounces for first-class mail, while international shipping carriers like DHL and FedEx often quote in grams or kilograms. A 3 oz letter weighs 85 g, while a 16 oz package weighs 453.6 g. Understanding this conversion helps you estimate shipping costs accurately across carriers.
Nutrition labels in the US list serving sizes in both ounces and grams, but many fitness apps default to grams. If your protein goal is 6 oz of chicken per meal, that's 170.1 g of protein-rich meat. Tracking in grams gives you more precise control over macronutrient intake.
Gold and silver are measured in troy ounces (31.1035 g), not avoirdupois ounces. A 1 oz gold coin weighs about 31.1 g, not 28.35 g. Always verify which ounce type you're dealing with when working with precious metals.
For rough estimates: multiply ounces by 28. For more precision, multiply by 30 and subtract about 5%. For example, 5 oz × 28 = 140 g (actual: 141.75 g). Or 5 × 30 = 150, minus 7.5 = 142.5 g — both close enough for cooking.
The avoirdupois system (everyday weights) and the troy system (precious metals) evolved separately over centuries. The avoirdupois ounce (28.35 g) is used for food, postage, and general goods, while the troy ounce (31.10 g) is used for gold, silver, platinum, and gemstones.
No. A fluid ounce (fl oz) measures volume, not weight. One US fluid ounce equals about 29.57 milliliters. The weight of a fluid ounce depends on the liquid's density. One fluid ounce of water weighs approximately 29.57 g, but one fluid ounce of honey weighs about 42 g.
One pound (16 ounces) equals exactly 453.59237 grams. This is useful when converting larger weights that are typically expressed in pounds.
The gram is part of the International System of Units (SI), which provides a universal, decimal-based measurement system. This consistency makes it ideal for scientific research, international trade, and precise manufacturing where reproducibility matters.
Use our free online Ounces to Grams converter for instant, accurate conversions every time.