How many grams are in one ounce?

There are exactly 28.349523125 grams in one avoirdupois ounce. In everyday use this is rounded to 28.35 g.

What is the exact conversion factor for ounces to grams?

The international avoirdupois ounce is defined as exactly 28.349523125 grams. This definition has been fixed by international agreement since 1959, so no rounding is involved — this converter uses the full exact value.

Is an ounce of gold the same as an ounce of flour?

No. Food, postal and everyday weights use the avoirdupois ounce (28.3495 g). Precious metals use the troy ounce (31.1035 g), which is about 10 % heavier. This tool converts the common avoirdupois ounce only.

How do I convert 4 oz to grams?

Multiply 4 by 28.349523125 to get 113.398 g — roughly 113.4 g. You can also type 4 into the Ounces field above for the instant result.

How many ounces is 100 g?

Divide 100 by 28.349523125 to get approximately 3.5274 oz. This converter handles that reverse calculation automatically when you type into the Grams field.

Is this the same as fluid ounces?

No. This tool converts weight ounces (mass) — the avoirdupois ounce used for food and postal weights. Fluid ounces measure volume, not mass. They are completely different units and cannot be directly compared without knowing the density of the substance.

Ounces to Grams Converter

Recipes, postal labels, nutrition panels and product listings regularly switch between ounces (oz) and grams (g) depending on which side of the Atlantic they came from. This free converter changes avoirdupois ounces to grams and back in real time — so you can follow an American recipe with metric scales, weigh a parcel in grams and read the result in ounces, or check that a food label makes sense in either unit.

Type a value in the Ounces field and the Grams field updates instantly. Type in the Grams field and the converter works in reverse. No button press needed — the result appears as you type.

How it works

The avoirdupois ounce (the everyday unit used for food, parcels and general commerce) is defined by international agreement as exactly:

1 oz = 28.349523125 g

To convert ounces to grams the tool multiplies by that constant. To go the other way it divides by the same constant. Because the definition is exact, no rounding is introduced at the conversion stage — rounding only occurs when displaying the result for readability.

The formula in full:

Ounces to grams: g = oz × 28.349523125
Grams to ounces: oz = g / 28.349523125

Note that this is the avoirdupois ounce. The troy ounce used for precious metals is larger at 31.1034768 g, and the fluid ounce is a unit of volume, not mass.

Worked example

You are following an American baking recipe that calls for 4 oz of butter. Your kitchen scales measure in grams. How much do you need?

4 × 28.349523125 = 113.398 g

Round to the nearest gram: 113 g.

Conversely, a parcel weighs 200 g and the courier’s price list is in ounces. How heavy is it in ounces?

200 / 28.349523125 = 7.0548 oz

Quick reference table

Ounces (oz)	Grams (g)
0.5 oz	14.1748 g
1 oz	28.3495 g
2 oz	56.699 g
4 oz	113.398 g
8 oz	226.796 g
16 oz (1 lb)	453.592 g
32 oz (2 lb)	907.185 g

16 oz equals one avoirdupois pound (453.592 g) — a useful anchor point for larger weights.

Formula note

The exact value 28.349523125 g comes from the definition of the international pound (0.45359237 kg exactly) divided by 16 (the number of ounces in a pound): 0.45359237 × 1000 / 16 = 28.349523125. This has been the legally binding definition in the UK, US, Canada, Australia and other Commonwealth countries since 1 July 1959. All conversions on this page are therefore mathematically exact — the only approximation is the number of decimal places shown on screen.