How many grains are in one ounce?

Exactly 437.5 grains equal one avoirdupois ounce. This is a fixed, exact conversion defined by the international yard and pound agreement of 1959.

Is this avoirdupois or troy ounce?

This tool uses the avoirdupois ounce (the everyday ounce used in the US and UK for food, postal weights, and most general purposes). Note that 1 troy ounce = 480 grains, while 1 avoirdupois ounce = 437.5 grains.

What is a grain used to measure?

Grains are most commonly used to measure bullet and gunpowder weights in ballistics, as well as gemstone weights and some pharmaceutical measurements. One grain equals approximately 64.8 milligrams.

How precise is the conversion?

The conversion factor (437.5 grains per ounce) is exact — no rounding is involved. The displayed result is rounded to 6 decimal places for readability, but the underlying calculation is fully precise.

Can I convert ounces back to grains?

Yes — multiply ounces by 437.5 to get grains. For example, 1 oz = 437.5 gr, 2 oz = 875 gr, 0.5 oz = 218.75 gr.

Grains to Ounces Converter

Name: Grains to Ounces Converter
Availability: InStock
Author: Nham Vu

Enter a weight in grains and instantly see the equivalent in avoirdupois ounces.

Enter Weight in Grains

Grains (gr)

Result

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avoirdupois ounces (oz)

Formula: ounces = grains ÷ 437.5

Common Conversions

Grains (gr)	Ounces (oz)

1 avoirdupois oz = 437.5 gr exactly • 1 troy oz = 480 gr

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Summary

Enter a weight in grains and instantly see the equivalent in avoirdupois ounces.

How it works

Enter the weight in grains into the input field.
The tool divides your value by 437.5 (the exact grains-per-ounce constant).
The result in ounces is displayed instantly.
Use the reference table below for common conversions at a glance.
Click "Copy Result" to copy the ounce value to your clipboard.

Use cases

Converting bullet or cartridge weights from grains to ounces for ballistic calculations.
Checking gemstone or precious metal weights in different units.
Pharmacy and apothecary unit conversions.
Reloading ammunition and verifying powder charges.
Academic or scientific unit conversion exercises.
Cooking or recipe conversions that reference grain measurements.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu