In 1 ounces there are 28,349.523125 milligrams. Meanwhile in 1 milligrams there are 0.0000352740 ounces. Keep reading to learn more about each unit of measure and how they are calculated. Or just use the Milligrams to Ounces calculator above to convert any number.
* Values rounded to 6 decimal places for readability
To convert ounces to milligrams (mg), use the standard avoirdupois ounce used in the U.S. and many other places.
Example conversions
This oz to mg conversion is useful for tiny weights, like medications, powders, and chemicals, where milligrams give better control than ounces.
There are 28,349.523125 milligrams (mg) in 1 ounce (oz) for weight (avoirdupois). That’s because 1 oz = 28.349523125 grams, and 1 gram = 1,000 mg.
Use this conversion:
This works for ounces by weight (the common oz used for food and packages).
Multiply the number of ounces by 28,349.523125.
Example:
For a quick estimate, you can use 1 oz ≈ 28,350 mg.
No. oz measures weight, while fl oz measures volume.
You can’t convert fluid ounces to milligrams unless you also know the density of the liquid (like water, oil, syrup).
Here are common conversions (weight ounces):
This is useful for small amounts like powders and supplements.
If you mean 1 oz by weight, then:
If you mean 1 fluid ounce of water, that’s volume. In mass, it’s close to:
Most ounce-to-milligram conversions use the avoirdupois ounce:
A troy ounce is used for some metals:
Make sure you know which ounce type you have before converting.
Yes. For many cooking and daily uses, this is fine:
For lab work, medicine, or detailed nutrition tracking, use the full value:
A milligram is very small:
Since 1 oz is about 28.35 g, converting to milligrams multiplies the number by 1,000, which makes the result much larger.
Use a simple mental math method:
Or use the common rounded value:
No, not for ounces by weight.
1 oz always equals 28,349.523125 mg.
It only changes when you start with fluid ounces, because volume depends on the substance’s density.
The Calculate Box tool to convert ounces to milligrams uses the open source script Convert.js to convert units of measurement. To use this tool, simply type a ounces value in the box and have it instantly converted to milligrams.