An avoirdupois ounce is 1/16 pound.
Ounces to Milligrams Converter — oz to mg
Convert Ounce (oz) to Milligram (mg) using the exact conversion factor (1 ounce = 28,349.52313 milligram). See the formula, worked examples, conversion table, history, and common uses.
Ounces to Milligrams converter
Converter
Cooking Converter
Convert cooking volume and mass units used in recipes and nutrition workflows.
Context values
Some unit families need one extra value for a physically accurate result.
Milligram is 0.001 gram units.
Result = input x 0.02834952313 / 1e-6.
Mass units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Ounces to Milligrams
Ounce and Milligram both show up in recipes, and converting between them matters whenever a recipe from one country's cookbook needs to be followed with another country's measuring tools. Ounce is most often used for us cooking and recipe measurement (small quantities).
Formula
milligrams = ounces × 28349.523125
This factor comes from each unit's defined relationship to the category's base unit: 1 ounce equals 0.028349523125 base units, and 1 milligram equals 0.000001 base units, so dividing one by the other gives the direct ounce-to-milligram factor of 28349.523125.
Simple example
1 oz × 28349.52313 = 28,349.52313 mg
1 ounce = 28,349.52313 milligrams.
Real-world example
2 oz × 28349.52313 = 56,699.04625 mg
2 ounces = 56,699.04625 milligrams.
Conversion table
| Ounce (oz) | Milligram (mg) |
|---|---|
| 0.25 oz | 7,087.380781 mg |
| 0.5 oz | 14,174.76156 mg |
| 1 oz | 28,349.52313 mg |
| 2 oz | 56,699.04625 mg |
| 4 oz | 113,398.0925 mg |
| 8 oz | 226,796.185 mg |
Reverse conversion: Milligram to Ounce
1 mg × 0.00003527396195 = 0.000035274 oz
1 milligram = 0.000035274 ounces.
ounces = milligrams × 0.0000352739619496
For a page dedicated to this direction, see Milligram to Ounce.
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.
Understanding the Milligram (mg)
Milligram is 0.001 gram units.
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 milligrams are in 1 ounce?
1 ounce equals 28,349.52313 milligrams, using the exact defined conversion factor rather than an estimate.
How do I convert ounce to milligram?
Multiply the ounce value by 28349.52313. The converter above does this instantly to whatever precision you set.
How do I convert milligram back to ounce?
Use the reverse factor: 1 milligram equals 0.000035274 ounces. You can also use the swap control in the converter above to flip the direction instantly.
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.
What is a milligram?
Milligram (mg) is a unit of cooking.
Is the ounce to milligram 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.
Where is the ounce still used today?
United States (cooking, postal, retail) United Kingdom (informal/retail use)