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Peptide calculator: reconstitution and dosage

Enter your vial, water and dose to see how many units to draw.

What does this peptide calculator do?

This peptide calculator does the reconstitution math for you: it turns your vial amount, water and dose into the number of units to draw on an insulin syringe.

You enter how much peptide is in the vial, how much bacteriostatic water you added and the dose you want. It works on U-100, U-50 and U-40 syringes, and it shows every step of the math so you can check it. It does not suggest doses. You bring the dose; it turns that dose into a mark on your syringe.

How to use the peptide calculator

Enter the amount of peptide in the vial and choose mg or mcg. The label on the vial tells you this.
Enter how much bacteriostatic water you added to the vial, in mL.
Enter your dose and choose mcg or mg.
Choose your syringe type (U-100 is the most common) and its size.
Read the result. Draw the liquid up to the mark shown, then check it against the math.

Already drew some units and want to know the dose? Use the units to mcg calculator. To convert mL and units on their own, use the syringe units converter.

How many units is 250 mcg?

It depends on how strong your mixed vial is. With a 5 mg vial and 2 mL of water, 250 mcg is 10 units on a U-100 syringe.

With a 10 mg vial and 2 mL of water, the same 250 mcg is 5 units, because each unit holds twice as much. With a 5 mg vial and 3 mL of water it is 15 units. That is why the calculator asks for your vial and water, not just the dose.

Worked examples with the math shown

Each example below was worked out by the calculator on this page, step by step.

5 mg vial, 2 mL water, 250 mcg dose

Convert the vial amount to mcg: 5 mg × 1,000 = 5,000 mcg
Concentration: 5,000 mcg ÷ 2 mL = 2,500 mcg/mL (2.5 mg/mL)
Volume to draw: 250 mcg ÷ 2,500 mcg/mL = 0.1 mL
Units to draw: 0.1 mL × 100 units/mL = 10 units
Amount in each unit: 2,500 mcg/mL ÷ 100 units/mL = 25 mcg per unit (0.025 mg)
Doses in the vial: 5,000 mcg ÷ 250 mcg = 20 full doses

Draw to the 10-unit mark on a U-100 syringe.

10 mg vial, 3 mL water, 500 mcg dose

Convert the vial amount to mcg: 10 mg × 1,000 = 10,000 mcg
Concentration: 10,000 mcg ÷ 3 mL = 3,333.33 mcg/mL (3.33333 mg/mL)
Volume to draw: 500 mcg ÷ 3,333.33 mcg/mL = 0.15 mL
Units to draw: 0.15 mL × 100 units/mL = 15 units
Amount in each unit: 3,333.33 mcg/mL ÷ 100 units/mL = 33.33 mcg per unit (0.03333 mg)
Doses in the vial: 10,000 mcg ÷ 500 mcg = 20 full doses

Draw 15 units on a U-100 syringe, halfway between the 14- and 16-unit marks.

5 mg vial, 1 mL water, 1 mg dose

Convert the vial amount to mcg: 5 mg × 1,000 = 5,000 mcg
Convert the dose to mcg: 1 mg × 1,000 = 1,000 mcg
Concentration: 5,000 mcg ÷ 1 mL = 5,000 mcg/mL (5 mg/mL)
Volume to draw: 1,000 mcg ÷ 5,000 mcg/mL = 0.2 mL
Units to draw: 0.2 mL × 100 units/mL = 20 units
Amount in each unit: 5,000 mcg/mL ÷ 100 units/mL = 50 mcg per unit (0.05 mg)
Doses in the vial: 5,000 mcg ÷ 1,000 mcg = 5 full doses

Draw to the 20-unit mark on a U-100 syringe.

Units to draw for common vial sizes

Find your vial size and water volume, then read across to your dose. Values are units on a 1 mL U-100 syringe, calculated by this site.

Units to draw on a U-100 syringe by vial, water and dose
Vial	Water	mcg per mL	100 mcg	250 mcg	500 mcg	1 mg
2 mg	1 mL	2,000	5	12.5	25	50
2 mg	2 mL	1,000	10	25	50	100
2 mg	3 mL	666.67	15	37.5	75	doesn't fit a 1 mL syringe
5 mg	1 mL	5,000	2	5	10	20
5 mg	2 mL	2,500	4	10	20	40
5 mg	3 mL	1,666.67	6	15	30	60
10 mg	1 mL	10,000	1*	2.5	5	10
10 mg	2 mL	5,000	2	5	10	20
10 mg	3 mL	3,333.33	3	7.5	15	30
15 mg	1 mL	15,000	0.7*	1.7*	3.3	6.7
15 mg	2 mL	7,500	1.3*	3.3	6.7	13.3
15 mg	3 mL	5,000	2	5	10	20

* Under 2 units, which is hard to measure. Adding more water makes the same dose easier to read. – means the dose is more than a 1 mL syringe holds.

How do you read your result on the syringe?

Hold the syringe at eye level and read the line where the flat top edge of the plunger's rubber stopper sits, not its pointed tip.

Insulin syringes are marked in units, not mL. On a U-100 syringe, 100 units equals 1 mL, so each unit is 0.01 mL.

10 units on a 1 mL U-100 syringe. The stopper's top edge sits on the 10 line.

The lines are spaced differently on each U-100 syringe size:

0.3 mL: holds 30 units, with a line every 0.5 units, numbered every 5.
0.5 mL: holds 50 units, with a line every 1 unit, numbered every 5.
1 mL: holds 100 units, with a line every 2 units, numbered every 10.

When your dose falls between two lines, the calculator tells you, for example "halfway between the 24- and 26-unit marks".

Frequently asked questions

What does a peptide reconstitution calculator do?

It turns your vial amount, water volume and dose into the number of units to draw on an insulin syringe. It first works out how strong the mixed vial is (the concentration), then how much liquid holds your dose, then where that volume sits on the syringe scale.

Does the calculator recommend doses?

No. The calculator only does the math for a dose you enter. It never suggests a dose for any product or condition. Ask a qualified healthcare professional about dosing.

How do I calculate peptide concentration?

Divide the amount of peptide in the vial by the water you added. A 5 mg vial mixed with 2 mL of water holds 2,500 mcg per mL. At that strength, a 250 mcg dose is 10 units on a U-100 syringe.

Does adding more water change the dose?

No. More water spreads the same amount of peptide through more liquid, so each unit holds less and you draw more units for the same dose. A 5 mg vial mixed with 2 mL of water holds 2,500 mcg per mL, while a 5 mg vial mixed with 3 mL of water holds 1,666.67 mcg per mL.

How many doses are in a vial?

Divide the amount in the vial by your dose and round down. A 5 mg vial holds 20 doses of 250 mcg. The calculator shows this as "Full doses in vial".

What does U-100 mean on a syringe?

It tells you how many units fit in 1 mL. U-100 means 100 units fill 1 mL, so each unit is 0.01 mL. U-40 means 40 units fill 1 mL, so each U-40 unit is a bigger volume.

What size syringe should I use?

Use the smallest syringe that holds your whole dose, because smaller syringes have finer marks. A 0.3 mL U-100 syringe holds 30 units and is often marked every half unit. A 0.5 mL U-100 syringe holds 50 units, and a 1 mL U-100 syringe holds 100 units with a line every 2 units.

Why does the calculator warn when a dose is under 2 units?

Very small amounts are hard to measure accurately by eye. If your dose is under 2 units, adding more water when you mix the vial makes the same dose take up more units, which is easier to read.

Can I use a U-40 or U-50 syringe with this calculator?

Yes. Choose the syringe type under "Syringe type" and the calculator uses the right scale. Never use U-100 numbers on a U-40 syringe, because the same number of units is a different volume.

See all peptide reconstitution questions