Ounces to Milligrams
An instant ounces-to-milligrams converter, with the formula and a reference table below.
| Ounces | Milligrams |
|---|---|
| 1 oz | 28349.523125 mg |
| 2 oz | 56699.04625 mg |
| 3 oz | 85048.569375 mg |
| 5 oz | 141747.615625 mg |
| 10 oz | 283495.23125 mg |
| 25 oz | 708738.078125 mg |
| 50 oz | 1417476.15625 mg |
| 100 oz | 2834952.3125 mg |
How to use
- Enter a value in the Ounces field.
- The Milligrams figure appears immediately — no button to press.
- Typing in the Milligrams field converts back to Ounces the same way.
- Use the reference table for the values that come up most often.
Ounces to Milligrams formula
The factor from ounces to milligrams is 28349.5231.
mg = oz × 28349.5231
Why this factor: the ounce and the milligram are both defined against the kilogram, so dividing one definition by the other gives 28349.5231 directly. Both definitions are set out in full below.
To go the other way, divide by 28349.5231 — or use the Milligrams to Ounces converter, which is the same calculation reversed.
Worked example
Given 150 oz, multiplying by 28349.5231 yields 4252428.46875 mg.
150 oz × 28349.5231 = 4252428.46875 mg
The converter above does this for any value you type, in either direction.
What is an ounce?
An ounce is one sixteenth of a pound, used for small weights in the US.
Definition: Exactly 28.349523125 grams — one sixteenth of the international avoirdupois pound.
Where it is used: Food packaging, postal weights, and coffee and spice quantities in the US.
Worth knowing: Not the same as a fluid ounce, which measures volume. Also distinct from the troy ounce (31.103 g) used for gold and silver.
What is a milligram?
A milligram is one thousandth of a gram — the standard unit for drug doses and micronutrients.
Definition: Exactly 1×10⁻⁶ kilogram by SI prefix definition.
Where it is used: Medication dosages, vitamin and mineral content, and analytical chemistry.
Ounces vs Milligrams
The ounce is an imperial unit while the milligram is a metric unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many milligrams are in an ounce?
One ounce equals 28349.5231 milligrams.
What is the formula to convert ounces to milligrams?
Multiply the number of ounces by 28349.5231. To reverse it, divide by 28349.5231 instead.
How do I convert milligrams back to ounces?
Divide by 28349.5231, which is the same as multiplying by 3.52739619e-05.
How many milligrams are in 10 ounces?
10 oz works out to 283495.23125 mg.
Is there anything to watch out for with ounces?
Not the same as a fluid ounce, which measures volume. Also distinct from the troy ounce (31.103 g) used for gold and silver.
How is the ounce defined?
Exactly 28.349523125 grams — one sixteenth of the international avoirdupois pound.