Ounces to Grams Converter

The ounce used here is the avoirdupois ounce, defined as 1/16 of a pound. In 1959 the US and Commonwealth countries fixed the avoirdupois pound at exactly 0.45359237 kg via the International Yard and Pound Agreement. Divide that by 16 and you get 28.349523125 g per ounce, rounded to 28.3495 g for everyday use. It isn't round because it comes from splitting an English trade weight into sixteenths, not from any metric-friendly design.

Divide the gram value by 28.3495, or use the quick shortcut of multiplying by 0.035. The shortcut is fine for cooking or shipping estimates, but if you need precision — for pharmacy dosing, jewelry, or lab work — use the full 28.349523125 g/oz factor rather than the rounded approximation.

The FDA's Nutrition Labeling and Education Act (NLEA) of 1994 requires most packaged foods sold in the US to declare net quantity in both customary (ounces or pounds) and metric (grams or kilograms) units. That's why a cereal box lists something like "NET WT 12 OZ (340g)" — the gram figure is the legally required metric equivalent, not a marketing add-on.

Weight (avoirdupois) ounces only — the kind used for food packaging, postal weight, and body weight. A fluid ounce measures volume, not mass, and doesn't convert to grams with this same 28.3495 factor since it depends on the density of whatever is being measured. If you're converting a recipe's liquid measurements, you need a volume converter instead.

Manufacturers often size products to a round metric number (100 g) and then convert to ounces for a US label, rather than the other way around. 100 g ÷ 28.3495 = 3.5274 oz, which gets rounded to 3.5 oz for label readability under FDA rounding rules for quantities under 4 oz. The label isn't wrong — it's a rounded conversion of a metric-first product, not a literal calculator output. If you need the precise figure for a recipe or lab measurement, recompute from the gram weight directly rather than trusting the rounded oz figure on the package.

No — there are three different "ounces" and only one of them equals 28.3495 g. The avoirdupois ounce (food, shipping, body weight) is 28.349523125 g. The troy ounce (gold, silver, other precious metals) is heavier at 31.1034768 g. And the US fluid ounce is a volume measurement, not a weight — one fluid ounce of water weighs about 29.57 g, but a fluid ounce of oil or honey weighs a different amount because it depends on density. This converter handles avoirdupois ounces only, which is what's printed on virtually all US food and retail packaging.

8 oz × 28.349523125 g = 226.796185 g, which you'd round to 227 g for baking purposes. For comparison, common baking amounts convert as: 4 oz = 113.398 g, 6 oz = 170.097 g, 10 oz = 283.495 g, and 16 oz (1 lb) = 453.592 g. Note that flour, sugar, and butter all have different volume-to-weight ratios, so this math only applies when the recipe specifies weight in ounces — if it lists volume ounces (measuring cups), you need a separate volume conversion instead.

"Ounce" traces back to the Latin "uncia," meaning a twelfth part — originally 1/12 of the Roman libra (pound). That 1/12 fraction survives today in the troy ounce, still used for precious metals, where 12 troy ounces make a troy pound. The avoirdupois system that dominates everyday US weights broke from that tradition, redefining the ounce as 1/16 of its pound instead of 1/12 — which is why 16 oz makes a pound at the grocery store, but 12 troy oz makes a pound at the jeweler's.

It depends entirely on the task. For cooking, rounding to the nearest whole gram (or even nearest 5 g) is plenty — a gram or two of flour won't change a recipe. For postal and shipping calculators, carriers typically round up to the nearest gram or even nearest 10 g bracket, so slight underestimates can bump you into a higher rate tier. For pharmacy, jewelry, or lab work, use the full 28.349523125 g/oz factor and keep at least three decimal places, since small errors compound when scaled up to larger quantities.