Grams to milligrams:
multiply by 1,000
Convert grams to milligrams for food labels, supplements and lab work, with a chart and the mix-ups that cost accuracy.
Calcylator Editorial Team
Updated · 5 min read
How many milligrams are in a gram?
There are exactly 1,000 milligrams in one gram. Milli means one thousandth, so a milligram is 0.001 g. Anything in grams becomes a number a thousand times bigger in milligrams.
The two units sit side by side on nutrition labels. Bulk quantities such as fat or carbohydrate are in grams, while small amounts such as salt, sodium or caffeine are in milligrams.
The gram is the basic everyday unit of mass in cooking and nutrition, and the milligram is its small companion for ingredients that are measured in tiny amounts. Salt, caffeine, vitamins and minerals are all examples. Because both units belong to the same metric ladder, converting is just a decimal shift of three places. Nonetheless, slips are common when a label mixes the two units, so it helps to put everything in one unit before you compare products or add up a daily total. Keep the factor of 1,000 in mind and you can read any label quickly, whichever of the two units it uses.
The grams to mg formula
- mg:
- mass in milligrams
- g:
- mass in grams
- 1,000:
- milligrams in one gram (exact)
Ingredient
0.35 g
Multiply
0.35 × 1,000
Mass in mg
350 mg
The decimal point moves three places to the right.
More examples: 2.5 g is 2,500 mg, and 7.5 g is 7,500 mg. Going the other way, a reading of 45,000 mg is 45,000 ÷ 1,000 = 45 g.
- Write the weight in grams.
- Move the decimal point three places to the right.
- Add zeros if there are not enough digits.
- Check: the mg figure must be 1,000 times larger.
Chart: grams to milligrams
| g | mg |
|---|---|
| 1 g | 1000 mg |
| 2 g | 2000 mg |
| 5 g | 5000 mg |
| 10 g | 10000 mg |
| 25 g | 25000 mg |
| 50 g | 50000 mg |
| 100 g | 100000 mg |
| 250 g | 250000 mg |
| 500 g | 500000 mg |
| 1000 g | 1000000 mg |
Where grams and milligrams come up
- Nutrition labels listing salt or sodium in milligrams alongside fat in grams.
- Pharmacy and first-aid, where a tablet strength such as 500 mg is half a gram.
- Chemistry practicals, where a balance reading of 0.2500 g is 250.0 mg.
- Caffeine tracking: a drink with 0.08 g of caffeine contains 80 mg.
A second reading: a label showing 2,300 mg of sodium is 2.3 g.
Quick sanity checks for grams to milligrams
Write the gram value with three decimal places. For example, 0.05 g becomes 0.050 g, and the three digits after the point are the milligrams: 50 mg.
For larger masses, 12 g is 12,000 mg and 1 kg is 1,000,000 mg.
If you have a mixed label with fat in grams and salt in milligrams, convert them to one unit before comparing.
Common mistakes when converting g to mg
- Dividing by 1,000 when going from grams to milligrams. The milligram number should be larger.
- Moving the decimal two places or four places instead of three.
- Mixing up mg and µg. A microgram is a thousandth of a milligram, so confusing them creates a factor-of-1,000 error.
- Reading 0.5 g as 5 mg. Half a gram is 500 mg.
This page covers unit conversion only. For medicine or supplement doses, follow the label and ask a health professional; it is not medical advice.
Common questions
How many milligrams are in a gram?
There are 1,000 milligrams in one gram. Milligrams are the smaller unit, so 5 grams is 5,000 mg and half a gram is 500 mg. Conversely, each milligram is one thousandth of a gram, or 0.001 g.
How do I convert grams to milligrams?
Multiply the grams by 1,000, which moves the decimal point three places to the right. For example, 2.5 g is 2,500 mg. The milligram figure is always 1,000 times the gram figure, so check that it looks much bigger.
How do I convert milligrams to grams?
Divide the milligrams by 1,000, moving the decimal point three places to the left. A 750 mg dose is 0.75 g. The gram figure is always smaller, and a thousandth of the milligram figure.
How many mg is 0.5 g?
Half a gram is 500 milligrams, since 0.5 × 1,000 = 500. Likewise 0.25 g is 250 mg and 0.1 g is 100 mg. It helps to remember that 1 g splits into one thousand equal milligrams.
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