Kilograms to Milligrams Converter

Kilograms to Milligrams

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

The Formula

`` milligrams = kilograms × 1000000 kilograms = milligrams × 0.000001 `

One kilogram is 1,000,000 milligrams, and one milligram is 1.0000e-6 kilograms.

Conversion Table

Kilograms	Milligrams
1 kg	1,000,000 mg
2 kg	2,000,000 mg
5 kg	5,000,000 mg
10 kg	10,000,000 mg
25 kg	25,000,000 mg
50 kg	50,000,000 mg
100 kg	100,000,000 mg
500 kg	500,000,000 mg
1,000 kg	1,000,000,000 mg

The Other Direction

Milligrams	Kilograms
1 mg	1.0000e-6 kg
2 mg	2.0000e-6 kg
5 mg	5.0000e-6 kg
10 mg	1.0000e-5 kg
25 mg	2.5000e-5 kg
50 mg	5.0000e-5 kg
100 mg	1.0000e-4 kg
500 mg	5.0000e-4 kg
1,000 mg	0.001 kg

What Each Unit Is

Kilograms (kg) — defined since 2019 by fixing the Planck constant — the SI base unit of mass. Originally the mass of a litre of water, then a platinum-iridium cylinder near Paris until 2019.

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

A Sense of Scale

• A litre of water is 1 kg
• A laptop is 1.5–2 kg
• Checked baggage allowance is often 23 kg
• A grain of sand is about 1 mg
• An aspirin tablet is 300–500 mg
• Nutrition labels use mg for sodium

Precision

The factor 1000000 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.

In Code

`javascript const kilogramToMilligram = (value) => value * 1000000; ``

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 kg with the factor truncated at each decimal place:

Decimals kept	Factor	137 kg becomes	Error
0	1000000	137,000,000	—
1	1000000	137,000,000	—
2	1000000	137,000,000	—
3	1000000	137,000,000	—
4	1000000	137,000,000	—

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 kilograms to three significant figures, the answer in milligrams is only good to three — writing more digits claims precision the measurement never had.