Ounces to Grams Converter

Related Calculators

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Ounce (oz): A unit of weight or mass used in the US. This converter uses the common avoirdupois ounce, not a fluid ounce.[3]

Gram (g): A metric unit of mass. One gram is one-thousandth of a kilogram.[1]

Avoirdupois ounce: The standard everyday ounce used for things like food, packages, and other weight measurements.[2]

Reverse check (oz): The ounce value you get after converting the gram result back to ounces. It helps you see whether rounding changed the displayed answer.

Rounding: The number of decimal places shown in Grams (g). The calculator uses the full conversion factor first, then rounds the display.

Mistake: Leaving Ounces (oz) blank and expecting Grams (g) to appear.
Fix: Enter a real number in Ounces (oz) , such as 1, 0.5, or 10.

Mistake: Typing words or symbols into Ounces (oz) , like "two oz".
Fix: Enter numbers only in Ounces (oz) , such as 2 or 2.25.

Mistake: Using fluid ounces from a drink recipe and reading the result as Grams (g) of weight.
Fix: Use this tool only for weight in Ounces (oz) . Check the Note if you are unsure about ounce type.

Mistake: Choosing Nearest whole gram in Show result as and then wondering why Reverse check (oz) is not exactly the same.
Fix: Switch Show result as to 2 decimal places , 4 decimal places , or Full calculator precision for a closer reverse check.

Mistake: Ignoring a negative value in Grams (g) after entering a negative Ounces (oz) number.
Fix: A negative result means your starting Ounces (oz) value was negative. Change the sign only if that was a typing mistake.

• This tool converts avoirdupois ounces to grams only. It does not convert fluid ounces because fluid ounces measure volume, not mass.
• The main math uses 1 oz = 28.349523125 g. If another class, worksheet, or industry rule uses a shorter factor, your final rounded value may differ slightly.
• The Reverse check (oz) can differ from your starting value when you choose stronger rounding, especially Nearest whole gram.
• Negative inputs are allowed for signed changes or differences. A negative gram result means the starting ounce value was negative.
• Very large entries can be displayed with commas, but values that overflow normal numeric limits should be treated as invalid input.

How the converter works

The calculator multiplies your Ounces (oz) value by the standard avoirdupois conversion factor to get Grams (g).

g = oz x 28.349523125

Then it converts the gram result back to ounces for the check output.

oz = g / 28.349523125

Rounding and display

Show result as changes only how many decimals are shown. The conversion uses the full factor first, and rounding happens after that. This is why the reverse check is usually closest when you choose 4 decimals or full precision.

Mini example

If you enter 1 ounce, the calculator multiplies 1 by 28.349523125.

g = 1 x 28.349523125 = 28.349523125

If you picked 2 decimal places, the displayed Grams (g) value becomes 28.35 g. The reverse check then uses the displayed gram value.

oz = 28.35 / 28.349523125 = 1.0000168...

That reverse-check result is very close to 1 oz, so the conversion looks reasonable.

Constants used

The calculator uses 1 avoirdupois ounce = 28.349523125 grams.[1][3] It also follows the SI definition that 1 gram = 0.001 kilogram.[1]

Assumptions used here

This tool assumes your ounce value is a weight or mass measurement in avoirdupois ounces. It does not estimate density, volume, packaging rules, or recipe-specific behavior, so real-world labels may round differently.