Ounces to Milligrams Converter

Ounces to Milligrams

Convert ounces (oz) to milligrams (mg). Both measure mass and weight, and the conversion comes up in cooking, shipping, fitness work.

The Formula

`` milligrams = ounces × 28349.523125 ounces = milligrams × 0.0000352739619496 `

One ounce is 28,349.52 milligrams, and one milligram is 3.5274e-5 ounces.

Conversion Table

Ounces	Milligrams
1 oz	28,349.52 mg
2 oz	56,699.05 mg
5 oz	141,747.62 mg
10 oz	283,495.23 mg
25 oz	708,738.08 mg
50 oz	1,417,476.16 mg
100 oz	2,834,952.31 mg
500 oz	14,174,761.56 mg
1,000 oz	28,349,523.13 mg

The Other Direction

Milligrams	Ounces
1 mg	3.5274e-5 oz
2 mg	7.0548e-5 oz
5 mg	1.7637e-4 oz
10 mg	3.5274e-4 oz
25 mg	8.8185e-4 oz
50 mg	0.001764 oz
100 mg	0.003527 oz
500 mg	0.017637 oz
1,000 mg	0.035274 oz

What Each Unit Is

Ounces (oz) — one sixteenth of a pound, or exactly 28.349523125 grams. From uncia, one twelfth — of the Roman libra, before avoirdupois moved it to one sixteenth.

Milligrams (mg) — one thousandth of a gram. The metric unit for doses and trace quantities.

A Sense of Scale

• A slice of bread is about 1 oz
• A tennis ball is 2 oz
• US recipes use ounces for dry goods
• A grain of sand is about 1 mg
• An aspirin tablet is 300–500 mg
• Nutrition labels use mg for sodium

Precision

The factor 28349.523125 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.

Watch Out For

• A fluid ounce measures volume, not mass, and the two are only interchangeable for water by coincidence of scale.

In Code

`javascript const ounceToMilligram = (value) => value * 28349.523125; ``

Where This Conversion Comes Up

• Cooking
• Shipping
• Fitness
• Medicine
• Manufacturing

How Many Decimals Do You Need?

Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 oz with the factor truncated at each decimal place:

Decimals kept	Factor	137 oz becomes	Error
0	28350	3,883,950	0.0017%
1	28349.5	3,883,881.5	—
2	28349.52	3,883,884.24	—
3	28349.523	3,883,884.65	—
4	28349.5231	3,883,884.66	—

A rule that holds for any conversion: round once, at the end. Rounding the factor and then multiplying compounds the error through every subsequent calculation, while carrying full precision and rounding the final answer does not.

The right number of significant figures is set by your input, not by the converter. If you measured ounces to three significant figures, the answer in milligrams is only good to three — writing more digits claims precision the measurement never had.