Mg to grams converter, milligrams, grams and micrograms.

To convert mg to grams, divide the milligrams by 1,000. So 500 mg is 0.5 g, 1,500 mg is 1.5 g and 5 mg is 0.005 g. That is the same as moving the decimal point three places to the left. The conversion is exact, so there is no rounding to worry about. This page does the sum for you and also gives micrograms and kilograms for the same amount.

How to use the converter

1. Type the amount in the Milligrams (mg) box, for example 500.
2. The big result shows Grams (g). The cards below it give micrograms and kilograms.
3. Type grams in the second box to get milligrams. For a different unit, the cards give micrograms and kilograms.
4. Click a row in Common values to load it. Use Decimals if you want a fixed number of places.
5. Press Copy result, Copy link or Print chart to keep the answer.

Where the 1,000 comes from

The SI prefix milli means one thousandth. The BIPM list of SI prefixes gives milli as 10⁻³, micro as 10⁻⁶ and kilo as 10³. NIST explains that the kilogram is the SI base unit of mass and, since compound prefixes are not allowed, prefixes for mass are attached to the gram, so it is 1 mg and not 1 microkilogram (NIST, metric SI prefixes). NIST Handbook 44 (2026), Appendix C lists 1 milligram as 0.001 gram exactly, 1 microgram as 0.000 001 gram exactly and 1 kilogram as 1,000 grams exactly. Pages checked 18 Oct 2026.

The shortcut, and its error

Move the decimal point three places to the left. 2,500 mg becomes 2.500, which is 2.5 g. 40 mg becomes 0.040, which is 0.04 g. 7 mg becomes 0.007 g. The shortcut is exact. Its only risk is slipping by one place, so count the zeros: grams has three fewer digits before the point than milligrams. An error of one place is a factor of ten, which is the mistake to avoid. A check is that the number of grams is always much smaller than the number of milligrams, a thousandth of it.

Worked examples

• 500 mg. 500 ÷ 1,000 = 0.5 g, which is 500,000 µg.
• 250 mg. 0.25 g. Four of them make 1 g.
• 1,200 mg. 1.2 g.
• 5 mg. 0.005 g, or 5,000 µg.
• 0.5 mg. 0.0005 g, which is 500 µg.

The prefix ladder from kilogram to microgram

Each step is a factor of 1,000. Knowing the ladder lets you convert between any two without a tool.

From mg to µg multiply by 1,000, and from mg to g divide by 1,000. 1 mg is 1,000 µg, and 1 g is 1,000 mg. A kilogram is 1,000,000 mg, which is a million.

Mistakes that are specific to mg and grams

The costly mistake on a label is mixing up mg and µg (often written mcg). They are a factor of 1,000 apart: 1 mg is 1,000 µg. When a label gives one unit and you want the other, convert it, but read the unit twice. The second is a decimal slip. 0.5 g is 500 mg and not 50 mg. The third is mass against concentration: mg is a mass, and mg per mL is a strength. A bottle that says 100 mg per 5 mL has 20 mg in each mL, and this converter cannot work that out from mg alone. The fourth is dosing. This page is arithmetic only and does not tell you how much of a medicine, vitamin or supplement to take. Follow the label, a doctor or a pharmacist for that.

Labels and recipes where mg to grams turns up

A label may list one item in mg and another in grams, and you may need both in the same unit to compare them. A figure of 2,300 mg is 2.3 g. Small scales read in mg or g. For weights in ounces see the Grams to ounces converter, and for pounds the Grams to pounds.

Check the answer, and jump more than one step

To check, multiply the grams by 1,000 and you should have the milligrams again: 0.5 g × 1,000 = 500 mg. For a bigger jump, count the steps on the ladder. From micrograms to grams is two steps, so divide by 1,000,000: 250,000 µg is 0.25 g. From kilograms to milligrams is two steps the other way, so multiply by 1,000,000: 0.002 kg is 2,000 mg. The cards under the result do these steps for the amount you type.

Decimals for very small amounts

Small milligram values give small gram values. 1 mg is 0.001 g, and 0.1 mg is 0.0001 g. The Auto setting adds places for small answers so that at least four digits show. If you want the same number of places in every row of the table, choose a number in Decimals, up to 8. Remember that a scale that reads to 1 mg cannot give a meaningful tenth of a milligram, however many places the result shows.

Who uses mg to grams

Students in a science class. Hobbyists who weigh small amounts. People comparing two labels that use different units. Anyone who needs to put a milligram value next to a gram value on one page. For a bigger weight in kilograms see the KG to LBS converter.