A grain is exactly 64.79891 milligrams.
Grains to Ounces Converter — gr to oz
Convert Grain (gr) to Ounce (oz) using the exact conversion factor (1 grain = 0.0022857143 ounce). See the formula, worked examples, conversion table, history, and common uses.
Grains to Ounces converter
Converter
Mass/Weight Converter
Convert SI mass, imperial weight, jewelry, atomic, and astronomy mass units.
Context values
Some unit families need one extra value for a physically accurate result.
An avoirdupois ounce is 1/16 pound.
Result = input x 6.479891e-5 / 0.02834952313.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Grains to Ounces
Weight conversions between Grain and Ounce come up constantly in everyday commerce, shipping, and cooking, since US packaging is usually labeled in pounds while most of the rest of the world uses kilograms. Specifically: A grain is exactly 64.79891 milligrams, and an avoirdupois ounce is 1/16 pound.
Formula
ounces = grains × 0.00228571428571
This factor comes from each unit's defined relationship to the category's base unit: 1 grain equals 0.00006479891 base units, and 1 ounce equals 0.028349523125 base units, so dividing one by the other gives the direct grain-to-ounce factor of 0.00228571428571.
Simple example
1 gr × 0.002285714286 = 0.0022857143 oz
1 grain = 0.0022857143 ounces.
Real-world example
50 gr × 0.002285714286 = 0.1142857143 oz
50 grains = 0.1142857143 ounces.
Conversion table
| Grain (gr) | Ounce (oz) |
|---|---|
| 1 gr | 0.0022857143 oz |
| 5 gr | 0.0114285714 oz |
| 10 gr | 0.0228571429 oz |
| 25 gr | 0.0571428571 oz |
| 50 gr | 0.1142857143 oz |
| 100 gr | 0.2285714286 oz |
Reverse conversion: Ounce to Grain
0.0022857143 oz × 437.5 = 1.000000006 gr
0.0022857143 ounces = 1.000000006 grains.
grains = ounces × 437.5
For a page dedicated to this direction, see Ounce to Grain.
Understanding the Grain (gr)
A grain is exactly 64.79891 milligrams.
Understanding the Ounce
Ounce (oz) measures mass. The avoirdupois ounce is 1/16 of a pound: exactly 28.349523125 grams. It is classified as a US/imperial customary unit.
Where it's used: United States (cooking, postal, retail) United Kingdom (informal/retail use)
Avoirdupois ounce vs. troy ounce. The everyday ounce (avoirdupois, 28.35 g) used for cooking and shipping is a different, smaller unit than the troy ounce (31.10 g) used for precious metals like gold and silver — this page uses the everyday avoirdupois ounce.
Uses of the Ounce today
- US cooking and recipe measurement (small quantities)
- US postal and shipping weight
- Precious metals (troy ounce, a related but distinct unit)
History of the Ounce
The ounce descends from the Roman 'uncia' (a twelfth part), inherited through medieval English weight systems; the avoirdupois ounce (for general goods, as opposed to the troy ounce for precious metals) became standard for everyday trade, fixed at exactly 28.349523125 g via the pound's 1959 international standardization.
Historical origin. Ounce was not the invention of a single named person; it developed through the process described above.
Ounce — sources
- NIST — International yard and pound (1959) — Basis for the modern ounce via the standardized pound.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many ounces are in 1 grain?
1 grain equals 0.0022857143 ounces, using the exact defined conversion factor rather than an estimate.
How do I convert grain to ounce?
Multiply the grain value by 0.002285714286. The converter above does this instantly to whatever precision you set.
How do I convert ounce back to grain?
Use the reverse factor: 1 ounce equals 437.5 grains. You can also use the swap control in the converter above to flip the direction instantly.
What is a grain?
Grain (gr) is a unit of mass/weight.
What is a ounce?
Ounce (oz) measures mass. The avoirdupois ounce is 1/16 of a pound: exactly 28.349523125 grams. It is classified as a US/imperial customary unit.
Is the grain to ounce conversion exact?
Yes. The avoirdupois ounce is 1/16 of a pound: exactly 28.349523125 grams. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between avoirdupois ounce vs. troy ounce?
The everyday ounce (avoirdupois, 28.35 g) used for cooking and shipping is a different, smaller unit than the troy ounce (31.10 g) used for precious metals like gold and silver — this page uses the everyday avoirdupois ounce.