Ounces to Milligrams Converter

What is an ounces to milligrams converter?

This tool converts a weight given in ounces (oz) into milligrams (mg). The ounce here is the avoirdupois ounce used for mass, not the fluid ounce used for volume, so the result describes how heavy something is rather than how much space it takes up. Type a value into either field and the matching amount appears in the other one instantly.

Milligrams are handy for very small masses, such as a vitamin dose or a tiny portion of an ingredient, while ounces are common for everyday weights in the United States and the United Kingdom. Converting between them lets you move smoothly between these two scales.

Formula

A single avoirdupois ounce weighs exactly 28.349523125 grams, and one gram contains 1000 milligrams. Combining the two gives the direct conversion:

$\text{Milligrams} = \text{Ounces} \times 28349.523125$

To go the other way, divide by the same factor:

$\text{Ounces} = \frac{\text{Milligrams}}{28349.523125}$

How to convert ounces to milligrams

1. Take the mass in ounces that you want to convert.
2. Multiply it by the base factor of 28349.523125 milligrams per ounce.
3. The product is the equivalent mass in milligrams.

Because the factor is exact, the conversion introduces no rounding of its own; any rounding you see comes only from the number of decimals you choose to display.

Worked examples

Example 1: 1 ounce to milligrams

$1 \times 28349.523125 = 28349.523125 \text{ mg}$

So one ounce equals 28349.523125 milligrams.

Example 2: 5 ounces to milligrams

$5 \times 28349.523125 = 141747.615625 \text{ mg}$

Example 3: 28349.523125 milligrams back to ounces

$\frac{28349.523125}{28349.523125} = 1 \text{ oz}$

This reverse check confirms that 28349.523125 milligrams is exactly 1 ounce.

FAQ

Is this the same as fluid ounces?

No. This converter handles the ounce as a unit of mass (avoirdupois ounce). A fluid ounce measures volume and converts to millilitres, not milligrams.

How many milligrams are in one ounce?

There are exactly 28349.523125 milligrams in one avoirdupois ounce. For related metric conversions see the mg to g converter or the grams to kilograms converter.