Free tool
Peptide calculator
Enter the peptide in the vial, the bacteriostatic water added and your target amount. The calculator returns the concentration, the volume to draw, the exact mark on a U-100 syringe and how many full draws the vial holds. A unit-conversion tool for laboratory preparation — for research use only.
1Reconstitution
2Target amount & syringe
This draw uses under 20% of a 50-unit barrel, where measurement error is highest. A smaller barrel gives wider spacing between markings.
- Concentration
- 5 mg/ml
- Target
- 250 mcg
- Full draws per vial
- 40
- Vial lasts
- Set frequency
This tool performs unit conversions for laboratory preparation only. It does not recommend an amount and gives no usage guidance of any kind. All products are for research use only and are not for human or veterinary use.
How to use the calculator
- 1Enter the peptide in the vial
Use the total mg printed on the vial label, e.g. 5 mg or 10 mg.
- 2Enter the bacteriostatic water added
The total volume of solvent in the vial after reconstitution, in ml.
- 3Enter the target amount
In mcg or mg, as set by your research protocol. The calculator never suggests one.
- 4Pick the syringe barrel
30, 50 or 100-unit U-100 barrel. The smallest one that holds the full draw is easiest to read.
- 5Read and double-check the result
Units to draw, ml, full draws per vial and — if you set a frequency — how long one vial lasts.
The maths behind it
Worked example
A 5 mg vial reconstituted with 2 ml of bacteriostatic water gives 2.5 mg/ml (2,500 mcg/ml). For a 250 mcg target: 250 ÷ 2,500 = 0.10 ml, which is 10 units on a U-100 syringe. The 5 mg vial holds 20 full draws of 250 mcg.
Load this example into the calculator →Water volume & concentration
Concentration and water volume are inversely related: double the water and the concentration halves, so the same amount takes twice the volume. Many researchers pick a water volume that makes the draw a round, easy number of units.
Syringe units & barrel size
“U-100” describes the scale: 100 units = 1 ml, so 1 unit = 0.01 ml. A 30, 50 or 100-unit barrel all read the same number for the same volume — smaller barrels simply space the markings further apart.
Accuracy on small draws
Reading error grows near the bottom of a barrel’s scale, roughly under 20% of its capacity, and below 2 units. The calculator flags these cases so you can switch barrel or adjust the water volume.
Frequently asked questions
What information does the peptide calculator need?+
Three numbers: the total peptide in the vial (mg), the volume of bacteriostatic water added (ml), and the target amount per draw (mcg or mg). From these it returns the concentration, the volume to draw in ml, the U-100 syringe units and the number of full draws in the vial.
How is the number of syringe units calculated?+
Concentration = mg in vial ÷ ml of water. Volume = target amount (mg) ÷ concentration. Units = volume (ml) × 100. Example: 5 mg in 2 ml is 2.5 mg/ml; 250 mcg (0.25 mg) ÷ 2.5 mg/ml = 0.1 ml = 10 units on a U-100 syringe.
Does adding more water change the amount of peptide?+
No. The amount of peptide in the vial is fixed. More water only lowers the concentration, so the same target amount needs a larger volume — which is often easier to measure accurately.
Are U-100 syringe units the same as IU?+
No. U-100 syringe units are volume markings: 100 units = 1 ml, so 1 unit = 0.01 ml. International Units (IU) describe biological activity and are specific to a compound. This calculator works only in mass (mg / mcg) and volume (ml).
Which syringe barrel size should I choose?+
Choose the smallest barrel that comfortably holds the whole draw. A 30-unit barrel spreads the markings further apart than a 100-unit barrel, so small volumes are easier to read. The unit number is the same on every U-100 barrel.
Why does the calculator warn about small draws?+
Measurement error rises at the bottom of a barrel’s scale — roughly the lowest 20% of its capacity — and anything under 2 units is very hard to read. If the draw is tiny, a smaller barrel or more water (a weaker concentration) gives a larger, more readable volume.
Can I use sterile water instead of bacteriostatic water?+
The arithmetic is identical for any compatible solvent. Which solvent is appropriate, and how long the solution remains stable, depends on the specific compound — follow the product documentation or your validated laboratory procedure.
How should reconstituted peptides be stored?+
Storage depends on the compound. As a general laboratory reference, sealed lyophilised vials are kept at −20°C for long-term storage, and reconstituted solutions at 2–8°C away from light. Swirl gently to dissolve rather than shaking.
Need bacteriostatic water or vials?
Third-party tested research peptides and lab essentials, dispatched from UK stock.
For laboratory research use only. This calculator performs concentration and volume arithmetic. It does not select an amount, establish sterility or stability, or replace compound-specific documentation. Not for human or veterinary use.