Ounces to Grams — Oz to G Conversion

A recipe lists $5$ oz of an ingredient, your scale reads grams, and you need the bridge. For the standard avoirdupois ounce used for food, packages, and body weight, that bridge is a single factor.

The formula and its symbols

so the rule is

The factor $28.349523125$ is the number of grams in one avoirdupois ounce. If your context is precious metals, stop and check first: a troy ounce is a different unit, so this oz-to-g factor does not apply automatically.

Why you multiply, not divide

An ounce is larger than a gram, so the count of grams must be bigger than the count of ounces. The mass itself never changes; only the unit label changes. Since each ounce holds about $28.35$ grams, you scale up by that factor, which means multiplying. Dividing would shrink the number, which is the wrong direction for going from a larger unit to a smaller one.

Worked example: convert $5$ oz to g

Start with the formula:

Multiply, keeping the unit in grams:

so

For everyday use, rounding is enough:

A nutrition label or kitchen estimate may round more than a lab measurement. The right number of decimal places depends on the situation.

Practice with a built-in check

Convert $12$ oz and $0.5$ oz yourself, then decide how much rounding each context deserves. Use this estimate to catch errors: $1$ oz is about $28.35$ g, so $10$ oz should land a little under $300$ g. If an answer comes out near $30$ g or $3000$ g, the decimal point slipped or you divided instead of multiplied. (Checking: $12 \times 28.35 \approx 340$ g, and $0.5 \times 28.35 \approx 14.2$ g.)

Calculation traps

Using the wrong kind of ounce. The standard ounce for everyday mass is not the troy ounce used for precious metals.

Dividing instead of multiplying. Going from ounces to grams multiplies, because each ounce contains about $28.35$ grams.

Rounding too early. Shortening the factor before multiplying lets the final answer drift more than necessary; round at the end.

You meet this conversion in cooking, nutrition labels, shipping, lab work, and product specs, anywhere one source gives mass in ounces and another expects grams.