Ounces to Grams Converter (oz to g)

This calculator converts a weight in ounces (oz) to grams (g) using the standard international avoirdupois ounce. Enter the number of ounces, and you get the equivalent mass in grams, plus the reverse conversion (grams to ounces) for convenience. The result is rounded to two decimal places, which is accurate for cooking, shipping, and most everyday uses.

Formula

The conversion factor is exact by definition: 1 avoirdupois ounce = 28.349523125 grams. To convert ounces to grams, multiply the number of ounces by this factor.

Symbolically: g = oz × 28.349523125

• oz = mass in ounces (avoirdupois)
• g = mass in grams

For the reverse, divide grams by the same factor: oz = g ÷ 28.349523125.

Worked Example

Using the default value of 8 ounces:

1. Start with the formula: g = oz × 28.349523125
2. Plug in 8 oz: g = 8 × 28.349523125
3. Multiply: g = 226.796185
4. Round to two decimal places: 226.80 grams

The calculator shows 226.80 g for 8 oz, matching this hand calculation.

Why the Ounce Has Several Definitions

Most of the world uses the metric system, but the ounce persists in the US and UK for food, postal mail, and precious metals. The critical distinction is between the avoirdupois ounce (used for everyday items) and the troy ounce (used for gold, silver, and gemstones). One troy ounce equals 31.1034768 grams, about 10% heavier than the avoirdupois ounce. This calculator uses the avoirdupois ounce, which is what you see on food labels and bathroom scales. If you are weighing precious metals, do not use this calculator—use a troy-ounce converter instead.

How to Use the Calculator

Enter a value in either the Ounces or Grams field. The other field updates instantly. The first output (Grams) is the headline answer; the second (Ounces) is the reverse conversion, useful when you have a gram weight and need ounces. The calculator works with decimals, so you can enter 0.5 oz for half an ounce or 2.25 oz for two and a quarter ounces. Negative values are not allowed because weight cannot be negative.

Common Mistakes and How to Avoid Them

• Using fluid ounces: Fluid ounces measure volume, not weight. One fluid ounce of water weighs about 1.04 ounces, but one fluid ounce of oil weighs less. This calculator is for weight only.
• Rounding too early: If you round 28.35 to 28 before multiplying, you introduce an error of about 0.02%—negligible for cooking but significant for precise lab work. Use the full factor when possible.
• Confusing troy and avoirdupois: As noted, troy ounces are heavier. Always check which system your recipe or package uses.
• Forgetting the decimal: 8 oz is not 8 g; it is 226.8 g. A common error is moving the decimal the wrong way when doing mental math.

When to Use This Conversion

You will need this conversion in several everyday situations:

• Cooking and baking: Many US recipes list ingredients in ounces, while digital scales in other countries show grams. Converting ensures accurate measurements, especially for flour and sugar.
• Postage and shipping: Postal rates are often quoted in ounces, but international forms may require grams.
• Fitness and nutrition: Food labels list serving sizes in grams, but you may weigh your portion in ounces on a kitchen scale.
• Science and education: Lab exercises often require converting between imperial and metric units.

Limits of the Formula

The conversion factor is exact, so the only limits come from rounding. For most purposes, two decimal places is more than enough. If you need extreme precision (e.g., for pharmaceutical compounding), use more decimal places or a scale that reads in milligrams. The calculator rounds to two decimals, which introduces a maximum error of 0.005 g—far below what a typical kitchen scale can detect.

Frequently Asked Questions

How many grams are in an ounce?

One avoirdupois ounce equals exactly 28.349523125 grams. For quick mental math, most people use 28.35 g per ounce, which is accurate to about 0.002%.

Is 100 grams the same as 3.5 ounces?

Yes, approximately. 100 g divided by 28.35 gives 3.527 oz. In cooking, this is often rounded to 3.5 oz, but for precise weighing, use the full decimal.

Why do some recipes use “oz� for both weight and volume?

In the US, “oz� can mean either avoirdupois ounces (weight) or fluid ounces (volume). A fluid ounce of water weighs about 1.04 oz, but for other liquids the weight differs. Always check if the recipe says “oz� (weight) or “fl oz� (volume).

What is the difference between a troy ounce and a regular ounce?

A troy ounce weighs 31.1034768 g, while a regular (avoirdupois) ounce weighs 28.349523125 g. Troy ounces are used for precious metals and gemstones; regular ounces are used for everything else. The difference is about 9.7%.

Can I use this calculator for fluid ounces?

No. This calculator only converts weight ounces to grams. To convert fluid ounces to grams, you need the density of the liquid. For water, 1 fluid ounce weighs about 29.57 g, but for oil it is about 27 g.

How do I convert ounces to grams without a calculator?

Multiply the number of ounces by 28.35. For example, 4 oz × 28.35 = 113.4 g. For a rough estimate, multiply by 30 and subtract 5%—this gives a close approximation.

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in oz | Ounces | oz | 8 | 0
in g | Grams | g | 0 | 0
out grams | Grams | g | oz * 28.349523125 | 2
out ounces | Ounces | oz | g / 28.349523125 | 2