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Grams to milligrams converter

Read a quantity in g, then express the same mass in mg. The units are defined below to avoid mixing similarly named standards.

≈ 1000 mg

Up to 12 significant digits are displayed; floating-point results are approximate. No value is saved.

Direct example

1 g ≈ 1000 mg.

Formula and calculation

mg = g × 1000

Substituting 1 g gives approximately 1000 mg. Definitions use the constants above; arithmetic uses browser floating point and displays at most 12 significant digits. The rounded table is not an instrument calibration or certified measurement.

Which units does this page use?

grams: one thousandth of a kilogram.

milligrams: one millionth of a kilogram.

When this direction is useful

Start here when your source record uses g for ingredient mass and small parcels, but the receiving specification is expressed in mg for small laboratory sample mass; not dosage advice. Enter the original quantity rather than reusing a previously rounded result. If your source uses mg, use the reverse converter instead.

Conversion table

Approximate displayed values, with the same definitions as the converter
grams (g)milligrams (mg)
00
11000
55000
1010000
100100000

Limits and interpretation

These are non-negative physical quantities; negative inputs are rejected. Converting a unit changes neither the measured object nor the original precision. Use a decimal dot; grouping commas are not accepted. No external rates, live data or account are involved.

Frequently asked questions

Can I convert the other way?

Yes. Convert milligrams to grams with the inverse equation. Rounding a result before converting it back can introduce a small difference.

Are these the same as every similarly named unit?

No. Check the two definitions above. International length, avoirdupois mass, US customary liquid measures and temperature readings are explicitly distinguished; an ambiguous label on a source document must be resolved first.

Where do the conversion definitions come from?

They use SI and defined customary conversion relationships. See the NIST Guide for the Use of SI. Output formatting is this tool's display policy, not extra measurement accuracy.

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