mL to Units Calculator

Q: Are units and IU the same?

For most practical dosing, units and international units (IU) are used the same way: both measure biological activity. What matters for conversion is the number of units per mL shown on the label.

A “unit” isn’t a measure of volume at all. It describes how much active medicine you’re getting, while milliliters describe how much liquid it comes in, and the only thing that connects the two is the concentration printed on the vial. Get that link wrong and a dose can be off by a factor of two, five or more.

This mL to units calculator makes the link explicit: pick the concentration, enter a volume or a dose, and see exactly how many units that is, how much liquid to draw up, and where the line falls on the syringe.

Enter a volume in mL (or a dose in units) and choose the concentration, and the calculator returns the matching units or mL, the reading on a U-100 insulin syringe and a picture of the syringe filled to the right line.

Important: this calculator is for general information and checking your math. It is not medical advice. Always follow the dose and instructions from your doctor, pharmacist or veterinarian, and use the syringe or pen made for your medication’s concentration.

What is a “unit” in medicine?

A unit (U, sometimes IU for international unit) measures the biological activity of a medicine rather than its weight or volume. Insulin, heparin, some vitamins, fertility hormones and several other drugs are dosed in units because what matters is their effect on the body, not how many milligrams are in the bottle.

A milliliter (mL) is simply a volume of liquid. To move between the two you need the concentration, written as units per mL. Insulin labelled U-100 contains 100 units in every milliliter; U-40 contains 40, U-500 contains 500.

mL to units formula

Converting mL to units is a single multiplication:

Units = Volume (mL) × Concentration (units per mL)

To find the volume for a dose, divide instead:

Volume (mL) = Units ÷ Concentration (units per mL)

For standard U-100 insulin there’s a handy shortcut: move the decimal point two places. 0.35 mL is 35 units, and 12 units is 0.12 mL.

If you mix a powder yourself, work out the concentration first:

Concentration = Total units in vial ÷ mL of liquid added

mL to units conversion chart

This table shows how many units are in common volumes at each standard insulin concentration.

Units per volume at common insulin concentrations.
Volume	U-40	U-100	U-200	U-300	U-500
0.01 mL	0.4 units	1 units	2 units	3 units	5 units
0.02 mL	0.8 units	2 units	4 units	6 units	10 units
0.05 mL	2 units	5 units	10 units	15 units	25 units
0.1 mL	4 units	10 units	20 units	30 units	50 units
0.15 mL	6 units	15 units	30 units	45 units	75 units
0.2 mL	8 units	20 units	40 units	60 units	100 units
0.25 mL	10 units	25 units	50 units	75 units	125 units
0.3 mL	12 units	30 units	60 units	90 units	150 units
0.4 mL	16 units	40 units	80 units	120 units	200 units
0.5 mL	20 units	50 units	100 units	150 units	250 units
0.6 mL	24 units	60 units	120 units	180 units	300 units
0.75 mL	30 units	75 units	150 units	225 units	375 units
0.8 mL	32 units	80 units	160 units	240 units	400 units
1 mL	40 units	100 units	200 units	300 units	500 units

Units to mL chart for U-100

Volume needed for common doses of U-100 insulin.
Dose	Volume (mL)	Smallest U-100 syringe that fits
1 units	0.01 mL	0.3 mL (30 units)
2 units	0.02 mL	0.3 mL (30 units)
5 units	0.05 mL	0.3 mL (30 units)
8 units	0.08 mL	0.3 mL (30 units)
10 units	0.1 mL	0.3 mL (30 units)
12 units	0.12 mL	0.3 mL (30 units)
15 units	0.15 mL	0.3 mL (30 units)
20 units	0.2 mL	0.3 mL (30 units)
25 units	0.25 mL	0.3 mL (30 units)
30 units	0.3 mL	0.3 mL (30 units)
35 units	0.35 mL	0.5 mL (50 units)
40 units	0.4 mL	0.5 mL (50 units)
50 units	0.5 mL	0.5 mL (50 units)
60 units	0.6 mL	1 mL (100 units)
75 units	0.75 mL	1 mL (100 units)
80 units	0.8 mL	1 mL (100 units)
100 units	1 mL	1 mL (100 units)

Insulin syringe sizes

U-100 insulin syringes are marked in units rather than mL, and they come in three common sizes. Choosing the smallest syringe that holds your dose makes it easier to measure accurately, because the markings are spaced further apart.

Common U-100 insulin syringe sizes. Exact markings vary by brand; check the barrel of your own syringe.

U-40 syringes are marked for 40 units per mL and are used mainly with veterinary insulin. U-500 syringes are made specifically for U-500 insulin. A syringe only reads correctly with the concentration it was designed for.

mL to units examples

Example 1: 0.25 mL of U-100 insulin

Units = 0.25 × 100 = 25 units

Example 2: a 30-unit dose of U-100 insulin

Volume = 30 ÷ 100 = 0.3 mL, which fills a 0.3 mL syringe exactly

Example 3: 0.2 mL of U-40 insulin

Units = 0.2 × 40 = 8 units
The same 0.2 mL of U-100 insulin would be 20 units, which is why the syringe must match the insulin

Example 4: a mixed vial

A vial contains 5,000 units of powder and you add 2 mL of liquid.

Concentration = 5,000 ÷ 2 = 2,500 units per mL
A 500-unit dose = 500 ÷ 2,500 = 0.2 mL
On a U-100 syringe, 0.2 mL is the 20 mark

Common concentrations

Label	Units per mL	Typically used with
U-40	40	Veterinary insulin for cats and dogs; U-40 syringes
U-100	100	The standard concentration for most human insulin; U-100 syringes and pens
U-200	200	Some concentrated insulins, supplied in pens
U-300	300	Some concentrated long-acting insulins, supplied in pens
U-500	500	Concentrated insulin for people who need large doses; dedicated U-500 pens or syringes

Safety tips

Match the syringe to the medicine. Use U-100 syringes with U-100 insulin and U-40 syringes with U-40 insulin. Using the wrong one changes the dose.
Concentrated insulins are dialed in units on their own pen, which already accounts for the concentration. Don’t draw them out with a regular syringe unless your healthcare provider has told you exactly how.
Read the label every time. Check the concentration on each new vial or pen, especially after a prescription change.
Double-check small doses. At U-100, a mistake of 0.1 mL is 10 units.
Ask your pharmacist if you’re unsure how to measure a dose.

Frequently asked questions

How many units are in 1 mL?

It depends on the concentration. U-100 insulin has 100 units in 1 mL, U-40 has 40 units and U-500 has 500 units. For other medicines, check the units per mL on the label.

How many units is 0.1 mL?

At U-100 concentration, 0.1 mL is 10 units. At U-40 it is 4 units, and at U-500 it is 50 units.

How do I convert mL to units?

Multiply the volume in mL by the concentration in units per mL. For example, 0.4 mL × 100 units/mL = 40 units.

How many mL is 10 units of insulin?

For U-100 insulin, 10 units is 0.1 mL. For U-40 insulin, 10 units is 0.25 mL.

Can I use a U-100 syringe for U-40 insulin?

It isn’t recommended. The markings on a U-100 syringe assume 100 units per mL, so the numbers won’t match a U-40 dose. Use a U-40 syringe, or ask your vet or pharmacist how to convert safely.

Are units and IU the same?

For most practical dosing, “units” and “international units (IU)” are used the same way: both measure biological activity. What matters for conversion is the number of units per mL shown on the label.

Related Calculators

mL to Units Calculator – Convert mL to Insulin Units (U-100 Chart)