A free peptide calculator for reconstitution, dosage and syringe units. Enter your vial size in mg or mcg, the bacteriostatic water you added, and the dose you want — it returns the exact mark to draw to, your concentration in mg/ml, doses per vial and cost per dose.
100 units per ml. Check the barrel — this is what almost every insulin syringe is.
U-100 insulin syringe · 50 unit barrel
Reconstitution is two pieces of arithmetic. First you work out the concentration of the solution, then you work out what volume of that solution contains your dose.
Concentration is the peptide in the vial divided by the water you added. A 10 mg vial with 2 ml of bacteriostatic water gives 5 mg per ml. Your injection volume is then the dose divided by that concentration. A 250 mcg dose is 0.25 mg, and 0.25 divided by 5 is 0.05 ml.
The last step is converting that volume into syringe units, because insulin syringes are not marked in millilitres. On a U-100 syringe, 100 units is 1 ml, so 0.05 ml is 5 units. That is the number you draw to.
| Water added | Concentration | 250 mcg dose | Reads as |
|---|---|---|---|
| 1 ml | 10 mg/ml | 0.025 ml | 2.5 units |
| 2 ml | 5 mg/ml | 0.05 ml | 5 units |
| 4 ml | 2.5 mg/ml | 0.1 ml | 10 units |
Every row delivers the same 250 mcg. The difference is how easy the number is to read. At 1 ml of water you are trying to hit 2.5 units, which sits between two marks on most barrels. At 4 ml the same dose lands on a clean 10. When a vial is expensive, people often choose the water volume that makes their usual dose land on a round number.
Insulin syringes are labelled by scale and by barrel size, and the two are easy to confuse. The scale is the U number printed on the barrel. U-100 means 100 units per millilitre and is what almost everyone uses. U-40 means 40 units per millilitre and is mostly sold for veterinary use. Drawing to “10 units” on a U-40 syringe gives two and a half times the volume it would on a U-100, so the scale matters more than any other setting on this page.
Barrel size is the total the syringe holds: 0.3 ml holds 30 units, 0.5 ml holds 50, and 1 ml holds 100. A smaller barrel spreads the same units across more space, so a 30 unit barrel is easier to read precisely for small doses. If a dose does not fit the barrel you selected, the calculator says so and suggests diluting further instead.
The calculator above answers your exact case. This chart is the version worth writing on a sticky note: the concentration you get from the vial sizes and bacteriostatic water volumes people actually use. Concentration is all you need to remember — every unit count follows from it.
| Vial | + 1 ml | + 2 ml | + 3 ml | + 5 ml |
|---|---|---|---|---|
| 2 mg | 2 mg/ml | 1 mg/ml | 0.67 mg/ml | 0.4 mg/ml |
| 5 mg | 5 mg/ml | 2.5 mg/ml | 1.67 mg/ml | 1 mg/ml |
| 10 mg | 10 mg/ml | 5 mg/ml | 3.33 mg/ml | 2 mg/ml |
| 15 mg | 15 mg/ml | 7.5 mg/ml | 5 mg/ml | 3 mg/ml |
| 30 mg | 30 mg/ml | 15 mg/ml | 10 mg/ml | 6 mg/ml |
A fuller version of this table, plus units-per-dose and the conversions worth memorising, is on the printable cheat sheet. To turn any of those into syringe units: divide your dose by the concentration to get millilitres, then multiply by 100. A 250 mcg dose at 5 mg/ml is 0.05 ml, which is 5 units. The same arithmetic is what a peptide mixing calculator or a dilution calculator performs — the names differ, the maths does not.
The powder in a vial is fragile. It is dried under vacuum and it dissolves without being shaken or forced.
If the solution stays cloudy, has visible particles, or changes colour, that is a reason to stop and check the vial and the supplier documentation rather than to continue.
The bacteriostatic water has its own shelf life, separate from the peptide you mix with it, and the two are easy to confuse — how long bac water lasts and whether it needs refrigerating.
Mixing up mg and mcg. One mg is 1,000 mcg. This single slip produces answers that are 1,000 times out. If the calculator tells you your dose is larger than the entire vial, this is almost always why.
Assuming every syringe is U-100. Check the barrel. U-40 syringes exist and they are marked with the same unit numbers.
Forgetting the water volume you used. A vial reconstituted at 2 ml and one at 3 ml need different unit counts for the same dose. Label the vial when you mix it.
Reading between marks. If your answer lands on something like 7.5 units, consider reconstituting at a volume that puts it on a whole number instead.
The calculator above works for any vial. These pages start with the right numbers already filled in and cover the details specific to that compound.
