Tools
Peptide reconstitution calculator
By An NayalLast reviewed
Mixing a vial is simple. The math to get from milligrams to units on a syringe is where people slip. Enter your vial, the water you added and the dose your protocol already calls for, and the calculator shows the units to draw.
Draw this much
10units
= 0.1 mL at 2.5 mg/mL
Math conversion only. This does not tell you what dose to take. Always verify with a licensed provider.
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Worked example
These are the numbers the calculator opens with: a 5 mg vial, 2 mL of bacteriostatic water, a 250 mcg dose and a 1 mL syringe.
- Convert the dose to milligrams: 250 mcg / 1000 = 0.25 mg.
- Work out the concentration: 5 mg / 2 mL = 2.5 mg/mL.
- Find the volume: 0.25 mg / 2.5 mg/mL = 0.1 mL.
- Turn it into units: 0.1 mL x 100 = 10 units.
So the result card reads 10 units, “= 0.1 mL at 2.5 mg/mL”. That fits easily in the 1 mL syringe, so there is no warning. Switch to the 0.3 mL syringe and the answer stays 10 units; only the fill bar changes, because 10 units is a third of that barrel instead of a tenth.
Change one input and watch the rest move. Put 1 mL of water in the same 5 mg vial and the concentration doubles to 5 mg/mL, so the same 250 mcg drops to 5 units. More water gives a weaker solution and a bigger draw. Less water gives a stronger solution and a smaller draw.
How the math works
The calculator runs three lines of arithmetic, the same ones behind every chart on this site.
concentration (mg/mL) = vial mg / water mL
draw (mL) = dose mg / concentration
draw (units) = draw mL x 100
The 100 comes from the syringe. Insulin syringes are marked U-100, which means 100 units per mL, so one unit is 0.01 mL. A unit is a volume mark, not an amount of peptide. How much peptide sits in one unit depends on the concentration you mixed.
If you enter the dose in mcg, the calculator divides by 1000 first so everything stays in milligrams. Units are rounded to one decimal place, the volume to three and the mg/mL figure to two.
The over-capacity warning is a straight comparison: if the draw in mL is larger than the syringe you picked (0.3, 0.5 or 1 mL), the fill bar turns red and the card says how many mL the draw needs. Until the vial, water and dose are all above zero, the calculator shows no result at all rather than a misleading one.
The peptide picker is a shortcut, not part of the math. It copies the first vial size and water volume listed on that peptide's card into the two boxes and leaves the dose alone. The reconstitution chart runs the same formulas for every common vial and water volume if you would rather read a table.
Questions people ask
How many units is 250 mcg?
It depends on how much water went into the vial. A 5 mg vial mixed with 2 mL of bacteriostatic water makes 2.5 mg/mL, so 250 mcg (0.25 mg) is 0.1 mL, which is 10 units on a U-100 insulin syringe. The same 250 mcg from a 10 mg vial mixed with 2 mL (5 mg/mL) is 0.05 mL, or 5 units.
How many units is 1 mg of peptide?
Divide 1 mg by your concentration and multiply by 100. At 2.5 mg/mL (5 mg in 2 mL) that is 0.4 mL, or 40 units. At 5 mg/mL it is 0.2 mL, or 20 units.
What happens if the draw is bigger than my syringe?
The calculator flags it as over capacity when the volume to draw is more than the syringe you picked holds: 0.3 mL (30 units), 0.5 mL (50 units) or 1 mL (100 units). The fix is arithmetic: a larger syringe, or a different water volume, which changes the concentration and so the draw.
Does picking a peptide change the math?
No. The picker only fills in a vial size and water volume that vendors commonly list, the same figures shown on each peptide card. It never fills in a dose, and the formula is the same for every peptide. If your vial is different, type your own numbers over it.
Pepteca is for education and information only. It does not provide medical advice, diagnosis, or treatment, and its calculators perform unit math only. Always verify with a licensed provider before starting, changing, or stopping any protocol. Many peptides are not approved for human use and may be regulated differently where you live.