This converter turns ounces into milligrams instantly, using the exact factor 1 ounce = 28349.52313 milligrams. 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. One thousandth of a gram, the standard unit for medication doses and nutrients.
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
28349.52313- The exact number of milligrams in one ounce
milligrams- The converted result
How it works, step by step
- Enter the number of ounces you want to convert.
- The value is multiplied by 28349.52313, the exact conversion factor.
- The result is displayed in milligrams, 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 28349.523. That gives 141,747.62 milligrams. A quick sanity check: one ounce is larger than one milligram, so the number should get bigger — and it does.
Converting 72 ounces
72 × 28349.523 = 2,041,165.67 milligrams. Working backwards, 2,041,165.67 ÷ 28349.523 returns 72 ounces, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many milligrams are in one ounce?
Exactly 28349.52313. 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 milligrams?
Milligrams = ounces × 28349.52313. To reverse it, divide instead: ounces = milligrams ÷ 28349.52313, which is the same as multiplying by 3.527396195e-05.
Is the ounce bigger than the milligram?
Yes. One ounce equals 28349.5 milligrams, so it is the larger unit.
Why does my answer differ slightly from other ounces to mg 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 milligram?
One thousandth of a gram, the standard unit for medication doses and nutrients.
Ounces to milligrams reference table
| Ounces | Milligrams |
|---|---|
| 0.5 oz | 14,174.76 mg |
| 1 oz | 28,349.52 mg |
| 2 oz | 56,699.05 mg |
| 3 oz | 85,048.57 mg |
| 5 oz | 141,747.62 mg |
| 10 oz | 283,495.23 mg |
| 15 oz | 425,242.85 mg |
| 20 oz | 566,990.46 mg |
| 25 oz | 708,738.08 mg |
| 50 oz | 1,417,476.16 mg |
| 75 oz | 2,126,214.23 mg |
| 100 oz | 2,834,952.31 mg |
| 250 oz | 7,087,380.78 mg |
| 500 oz | 14,174,761.56 mg |
| 1000 oz | 28,349,523.13 mg |
Exact factor: 1 ounce = 28349.52313 milligrams. Values rounded for display.