Unit Conversion

Mass Conversion Calculator

Converts a mass between micrograms, milligrams, grams, kilograms, ounces and pounds — for doses, weighing and body weight.

In gram (g)

0.1g

100 mg = 0.1 g

Pharmacy note

For oral solid dosage forms, typical tablet strengths range from 1mg to 1000mg

Convert

Mass to convert (mg)

Any positive number. Decimals are fine — 0.25, 2.2, 1500.

From

Precision

Decimal places shown. Very large or small answers switch to scientific notation.

Common pharmacy conversions

In every unit

100 mg expressed in each unit.

Microgram (mcg)1.000e+5mcg

Milligram (mg)100mg

Input

Gram (g)0.1g

Result

Kilogram (kg)1.000e-4kg

Ounce (oz)0.0035oz

Pound (lb)2.205e-4lb

Conversion factor1 mg = 1000.000000 g

Reference

Common equivalents

1 kilogram (kg)2.20462 pounds (lb)

1 pound (lb)453.592 grams (g)

1 ounce (oz)28.3495 grams (g)

1 grain (gr)64.7989 milligrams (mg)

1 gram (g)1000 milligrams (mg)

Metric system

1 kg = 1000 g

1 g = 1000 mg

1 mg = 1000 mcg

Base unit: gram (g)

Imperial system

1 lb = 16 oz

1 oz = 28.35 g

1 lb = 453.59 g

1 grain = 64.8 mg

Apothecary (pharmacy)

1 scruple = 20 grains

1 drachm = 60 grains

1 ounce (apoth) = 480 grains

1 pound (apoth) = 5760 grains

result = value × (mg in 1 “from” unit) ÷ (mg in 1 “to” unit)

Every unit is first turned into milligrams, then divided into the target unit. Going through one base unit means only one factor per unit is needed, instead of one for every pair.

1 mcg0.001mg

1 mg1mg

1 g1000mg

1 kg1000000mg

1 oz28349.5231mg

1 lb453592.37mg

100 × 1 ÷ 1000 = 0.1 g

Guide: Pharmaceutical Dose Calculations: Units, Body Weight and Body Surface AreaThe concept in full, with practice questions.

References

Bureau International des Poids et Mesures. The International System of Units (SI Brochure). 9th ed. Sèvres: BIPM; 2019. Source
Stockton SJ. Stoklosa and Ansel's Pharmaceutical Calculations. 16th ed. Philadelphia: Wolters Kluwer; 2021.

Common questions

1000. Each step in the metric ladder — kg, g, mg, mcg — is a factor of 1000, so moving one step down multiplies by 1000 and one step up divides by 1000.

Answers of 10,000 or more, or smaller than 0.001, are shown in scientific notation: 5.000e-10 means 5.000 × 10⁻¹⁰. It keeps very large and very small numbers readable without a long run of zeros.

Yes. Weight-based doses (mg/kg) are written per kilogram. Divide pounds by about 2.2046 — or use this calculator — and dose from the kilogram figure.

No. This calculator uses the avoirdupois ounce (28.35 g), the everyday unit. The apothecary ounce is 480 grains, about 31.1 g, and appears only in old formulas.

An old apothecary unit of about 64.8 mg, still seen on some aspirin and thyroid labels. It is listed in the reference section rather than the converter.

About this calculator

Drug doses are written in micrograms, milligrams or grams, while body weight may arrive in pounds. A slipped decimal point between these units is one of the most common — and most dangerous — dosing errors, so it pays to convert deliberately and check the answer.

Use it when

Turning a prescribed dose into the units printed on the label

Converting a patient's weight from pounds to kilograms

Weighing ingredients for a compounded preparation

Checking a mcg ↔ mg step for a potent drug

Rounding

Use 4+ decimals for compounding

Use 2-3 decimals for dosing

Always round at final step

Watch out for

Write “mcg”, not “µg” — a handwritten µ is easily misread as “m”

Never add a trailing zero (5.0 mg) or omit a leading one (.5 mg)

Apothecary ounces and pounds differ from the avoirdupois units used here

Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy