How to calculate concentration in mg/mL
Divide the total amount in mg by the total volume in mL. A label that reads “50 mg/5 mL” means 50 mg in every 5 mL, which is 10 mg/mL; the FDA uses the same arithmetic in its own example, 100 mg/20 mL = 5 mg/mL.[1]
concentration (mg/mL) = total amount (mg) ÷ total volume (mL)
If the amount is in grams, multiply by 1,000 first; if it is in micrograms, divide by 1,000 (1 g = 1,000 mg; 1 mg = 1,000 mcg).[2] If a medicine is mixed from a powder, use the final strength given on the label or by your pharmacist.
mg/mL calculator: common label totals
Most labels print a total amount in a total volume. These are the same strengths written as mg per mL.
| Label total | mg/mL | mcg/mL | mg per U-100 unit |
|---|---|---|---|
| 10 mg in 1 mL | 10 | 10,000 | 0.1 |
| 10 mg in 2 mL | 5 | 5,000 | 0.05 |
| 20 mg in 2 mL | 10 | 10,000 | 0.1 |
| 50 mg in 5 mL | 10 | 10,000 | 0.1 |
| 100 mg in 20 mL | 5 | 5,000 | 0.05 |
| 125 mg in 5 mL | 25 | 25,000 | 0.25 |
| 250 mg in 5 mL | 50 | 50,000 | 0.5 |
| 500 mg in 10 mL | 50 | 50,000 | 0.5 |
| 1 mg in 10 mL | 0.1 | 100 | 0.001 |
Converting between concentration units
1 mg/mL equals 1,000 mcg/mL, 1 g/L and 0.1% w/v. The conversions follow from the metric prefixes: a litre is 1,000 mL and a gram is 1,000 mg.[3][2]
| mg/mL | mcg/mL | g/L | % w/v | mg per U-100 unit |
|---|---|---|---|---|
| 0.1 | 100 | 0.1 | 0.01 | 0.001 |
| 0.5 | 500 | 0.5 | 0.05 | 0.005 |
| 1 | 1,000 | 1 | 0.1 | 0.01 |
| 2 | 2,000 | 2 | 0.2 | 0.02 |
| 5 | 5,000 | 5 | 0.5 | 0.05 |
| 10 | 10,000 | 10 | 1 | 0.1 |
| 25 | 25,000 | 25 | 2.5 | 0.25 |
| 50 | 50,000 | 50 | 5 | 0.5 |
| 100 | 100,000 | 100 | 10 | 1 |
- mcg/mL: multiply mg/mL by 1,000.
- g/L: the same number as mg/mL (1,000 mg per 1,000 mL).
- % w/v: divide mg/mL by 10.
- Per syringe unit: divide mg/mL by 100, because a U-100 unit is 0.01 mL.[4]
Percent w/v explained
Percent weight-in-volume is grams per 100 mL: the FDA describes w/v as the mass in grams of solute in 100 mL of solution.[1] So 1% w/v is 1 g in 100 mL, which is 10 mg/mL, and 0.5% is 5 mg/mL.
mg/mL = % w/v × 10 · % w/v = mg/mL ÷ 10
Using the concentration
Once you know the concentration, every other conversion is one step. The Institute for Safe Medication Practices recommends writing a single drug's dose in weight, not volume alone, so keep the mg in view as well as the mL.[5]
- Dose in mg to volume: mg to mL calculator.
- Dose in mg to the line on an insulin syringe: mg to units.
- What a syringe reading contains: units to mg.
- Doses in micrograms: mcg to units.
Frequently asked questions
How do you calculate concentration in mg/mL?
Divide the amount in mg by the volume in mL. 20 mg in 4 mL is 5 mg/mL.
What is 1% in mg/mL?
1% weight-in-volume is 1 g per 100 mL, which is 10 mg/mL.
How do I convert mg/mL to mcg/mL?
Multiply by 1,000. 2.5 mg/mL is 2,500 mcg/mL.
Is mg/mL the same as g/L?
Yes, numerically: 1 mg/mL is 1,000 mg in 1,000 mL, which is 1 g per litre.