This converter turns ounces into grains instantly, using the exact factor 1 ounce = 437.5 grains. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
The avoirdupois ounce, exactly 28.349523125 grams — standard in US recipes. The oldest English mass unit, now used for bullets, arrows and propellant charges.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
ounces- The amount you are converting, measured in ounces
437.5- The exact number of grains in one ounce
grains- The converted result
How it works, step by step
- Enter the number of ounces you want to convert.
- The value is multiplied by 437.5, the exact conversion factor.
- The result is displayed in grains, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 ounces
Multiply 5 by 437.5. That gives 2,187.5 grains. A quick sanity check: one ounce is larger than one grain, so the number should get bigger — and it does.
Converting 72 ounces
72 × 437.5 = 31,500 grains. Working backwards, 31,500 ÷ 437.5 returns 72 ounces, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many grains are in one ounce?
Exactly 437.5. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert ounces to grains?
Grains = ounces × 437.5. To reverse it, divide instead: ounces = grains ÷ 437.5, which is the same as multiplying by 0.002285714286.
Is the ounce bigger than the grain?
Yes. One ounce equals 437.5 grains, so it is the larger unit.
Why does my answer differ slightly from other ounces to grains converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a ounce?
The avoirdupois ounce, exactly 28.349523125 grams — standard in US recipes.
What is a grain?
The oldest English mass unit, now used for bullets, arrows and propellant charges.
Ounces to grains reference table
| Ounces | Grains |
|---|---|
| 0.5 oz | 218.75 gr |
| 1 oz | 437.5 gr |
| 2 oz | 875 gr |
| 3 oz | 1,312.5 gr |
| 5 oz | 2,187.5 gr |
| 10 oz | 4,375 gr |
| 15 oz | 6,562.5 gr |
| 20 oz | 8,750 gr |
| 25 oz | 10,937.5 gr |
| 50 oz | 21,875 gr |
| 75 oz | 32,812.5 gr |
| 100 oz | 43,750 gr |
| 250 oz | 109,375 gr |
| 500 oz | 218,750 gr |
| 1000 oz | 437,500 gr |
Exact factor: 1 ounce = 437.5 grains. Values rounded for display.