Ounces to Milligrams
Convert ounces to milligrams instantly. 1 oz = 28349.523125 mg. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert ounces to milligrams
To convert ounces to milligrams, multiply by 28349.523125. The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
mg = oz × 28349.523125
Ounces to Milligrams conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Ounces | Milligrams |
|---|---|
| 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 |
| 20 oz | 566,990.46 mg |
| 25 oz | 708,738.08 mg |
| 50 oz | 1,417,476.16 mg |
| 100 oz | 2,834,952.31 mg |
| 500 oz | 14,174,761.56 mg |
| 1,000 oz | 28,349,523.13 mg |
What is a ounce?
A sixteenth of a pound, exactly 28.349523125 g.
What is a milligram?
A thousandth of a gram. Standard for medication strength.
The formula
mg = oz × 28349.523125
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Ounces to Milligrams
- Type the number of ounces you want to convert.
- Read the result in milligrams straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked milligrams to ounces page.
Ounces to Milligrams — frequently asked questions
How many milligrams are in a ounce?
One ounce equals 28349.523125 mg. mg = oz × 28349.523125
What is the formula to convert ounces to milligrams?
The formula is mg = oz × 28349.523125. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert milligrams back to ounces?
Divide instead of multiplying: one milligram is 3.5274e-05 oz. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this ounces to milligrams free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 15, 2026 · Calculation runs client-side · No data collected · Report an error