Ounces to Milligrams Converter
Enter the weight in ounces below to convert it to milligrams.
Convert Ounces to Milligrams
Enter a value in ounces (oz) to convert to milligrams (mg).
Ounce to Milligram Conversion Table
Table showing various ounce measurements converted to milligrams. Click any preset value or arrow to load it into the converter.
| Ounces (oz) | Milligrams (mg) |
|---|---|
| 1 oz | 28,349.523125 mg |
| 2 oz | 56,699.04625 mg |
| 2.5 oz | 70,873.8078125 mg |
| 5 oz | 141,747.615625 mg |
| 10 oz | 283,495.23125 mg |
| 15 oz | 425,242.846875 mg |
| 20 oz | 566,990.4625 mg |
| 25 oz | 708,738.078125 mg |
| 30 oz | 850,485.69375 mg |
| 50 oz | 1,417,476.15625 mg |
How to Convert Ounces to Milligrams
To convert ounces to milligrams, multiply the weight by the following conversion ratio: 28,349.523125 milligrams/ounce.
Since one ounce is equal to 28,349.523125 milligrams, you can use this simple formula to convert:
The weight in milligrams is equal to the weight in ounces multiplied by 28,349.523125.
For example, here's how to convert 5 ounces to milligrams using the formula above.
How Many Milligrams Are in an Ounce?
There are 28,349.523125 milligrams in an ounce, which is why we use this value in the formula above.
Our ounce to milligram calculator automatically converts your weight measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
Ounces and milligrams are both units used to measure weight. Keep reading to learn more about each unit.
What Is an Ounce?
An ounce is a unit of weight equal to 0.0283495 kilograms (kg), the base unit for weight. Equal to 1/16 of a pound (approx. 28.3495 grams). [1]
The ounce is classified as a US customary and imperial unit of weight. Ounces can be abbreviated as oz; for example, 1 ounce can be written as 1 oz.
When working with ounces (oz) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, ounces (oz) are widely used across standard weight applications within US customary and imperial workflows, engineering documentation, and technical data sheets.
What Is a Milligram?
A milligram is a unit of weight equal to 1/1,000,000 of a kilogram (0.000001 kg). One-thousandth of a gram (10⁻⁶ kg). [2]
The milligram is classified as a metric and SI-compatible unit of weight. Milligrams can be abbreviated as mg; for example, 1 milligram can be written as 1 mg.
In the metric system, "milli" is the standard SI prefix for thousandths, or 10⁻³. This makes the milligram (mg) a convenient decimal multiple of the gram (g).
In practice, milligrams (mg) are widely used across fine-tolerance laboratory, analytical, and micro-scale weight measurements within SI metric workflows, engineering documentation, and technical data sheets.
When converting weight between ounces (oz) and milligrams (mg), keep full floating-point precision (1 oz = 28,349.523125 mg; 1 mg = 0.000035274 oz) during intermediate calculations and round only the final milligram figure to match your instrument tolerance.
More Ounce & Milligram Conversions
Need to calculate in the opposite direction? Use our milligrams to ounces calculator to switch your starting unit immediately. You can also explore related tools such as converting milligrams to ounces, converting micrograms to milligrams, or converting grams to milligrams.
Convert from Ounces
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Frequently Asked Questions
References
- [1]NIST OWM StandardNIST OWM (SI Units — Mass)·Mass & Weight Metrology Standard — Ounces (oz) to Milligrams (mg)
- [2]NIST HB 44 SpecificationNIST HB 44 (NIST Handbook 44 (Current Ed.))·Unit Specifications: Ounce (oz) & Milligram (mg)
- [3]BIPM ReferenceBIPM (SI Base Unit: Kilogram (kg))·Conversion Factors & Mathematical Basis (oz to mg)