Peptide Calculator
Type in what is on the vial label, how much water you added, and the dose you want to work out. You get the draw in units, the concentration of your mix, and how many doses the vial holds. Those three answers cover almost every question people ask about a mixed vial.
Units measure volume, not dose. The same units on a different mix are a different dose.
The link holds only the numbers you typed. No account, no tracking, nothing else.
How this is worked out
Nothing clever happens behind the scenes. Using example A from the table below, a 5 mg vial mixed with 2 mL of water:
- Concentration: 5,000 mcg divided by 2 mL gives 2,500 mcg per mL.
- Draw volume: a 250 mcg dose divided by that concentration gives 0.1 mL.
- Units: 0.1 mL times 100 gives 10 units on a U-100 syringe. The vial holds 20 doses of that size.
Change any number in the calculator and all three steps redo themselves. If you would rather decide the draw first and have the water worked out for you, switch the mode to "Work out the water for the draw I want".
Worked examples
| Vial | Water | Dose | Concentration | Draw | Units | Doses per vial | |
|---|---|---|---|---|---|---|---|
| A | 5 mg | 2 mL | 250 mcg | 2,500 mcg/mL | 0.1 mL | 10 | 20 |
| B | 10 mg | 2 mL | 2.5 mg | 5,000 mcg/mL | 0.5 mL | 50 | 4 |
| C | 10 mg | 1 mL | 2 mg | 10,000 mcg/mL | 0.2 mL | 20 | 5 |
| D | 5 mg | 3 mL | 250 mcg | 1,667 mcg/mL | 0.15 mL | 15 | 20 |
The table is calculated by the same engine as the tool, at the moment this page is built. Type any row into the calculator and you will get the same row back.
Blend mode: more than one compound in the vial
Some vials hold two or more compounds in one powder. Every draw from a vial like that carries all of them, in proportion to how much of each went in. People get caught out because they work out the draw for one compound and forget the draw also delivers the others.
Enter each compound below, the water added to the shared vial, and a dose for one of them. The result lists what the draw delivers of every compound, so nothing rides along uncounted.
That one draw () delivers:
Units measure volume, not dose. In a shared vial, every draw carries every compound in it.
The link holds only the numbers you typed. No account, no tracking, nothing else.
mg to mcg converter
Most errors in this maths start here. One milligram is 1,000 micrograms, so a dose written in the wrong unit is out by a factor of a thousand, not by a rounding error. Convert first if you are ever unsure which one your dose is in.
U-100 and U-40 syringes are not interchangeable
A unit is not a fixed amount of liquid. It depends on the syringe. U-100 syringes hold 100 units per mL, so one unit is 0.01 mL. U-40 syringes hold 40 units per mL, so one unit is 0.025 mL, two and a half times as much. Fill a U-40 syringe to a number you got from a U-100 calculator and you have drawn two and a half times the volume you meant to.
Everything on this site is U-100, which is the standard for the syringes sold for this purpose. Check the printing on your barrel anyway. It takes two seconds.
Where people go wrong with this maths
Treating units as a dose is the big one. "I draw 10 units" tells you nothing until you know the concentration, because 10 units is just 0.10 mL of whatever happens to be in the vial. Always pair a unit number with the mix it came from.
Then there is the mg and mcg slip. 250 mcg typed as 250 mg is a thousandfold error, and it happens because the two look alike on a label. The result panel on the calculator shows your dose in both units for exactly this reason. Read that line before you trust the units.
Last, remember what the calculator cannot know. It uses the amount printed on your vial's label. If a vial is underfilled, or the label is wrong, the arithmetic is still right and the draw is still wrong. No calculator can test what is in the powder.
Common questions
How do I work out how many units to draw?
Divide the vial amount by the water to get the concentration. Divide your dose by the concentration to get the volume in mL. Multiply by 100 and you have units on a U-100 syringe. Or just use the calculator above, which is those three steps with the typing done for you.
What is the "perfect draw" mode?
It flips the question around. Instead of telling it the water and getting a draw, you tell it the draw you want, say 20 units, and it works out how much water gets you there. It rounds the water to the nearest 0.1 mL (nobody can measure more precisely than that) and then recalculates, so the units it shows are the units that water amount really gives you.
How many doses are in my vial?
Vial amount divided by dose. A 5 mg vial taken 250 mcg at a time holds 20 doses, because 5 mg is 5,000 mcg and 5,000 divided by 250 is 20. The calculator shows this under "doses per vial", along with any leftover amount that is too small to be a full dose.
Does the syringe size change the answer?
The units stay the same. A 0.3, 0.5 and 1 mL U-100 syringe all count 100 units per mL. What changes is whether your draw fits at all. A 60 unit draw physically cannot go into a 30 unit syringe, and the calculator will tell you when you have picked a combination like that.
What is the difference between U-100 and U-40 syringes?
U-100 syringes count 100 units per mL. U-40 syringes, mostly sold for pet insulin, count 40 units per mL, so one U-40 unit is a bigger volume (0.025 mL instead of 0.01 mL). Every tool here works in U-100. If your syringe says U-40 on the barrel, unit numbers from this site do not apply to it.
Why is my dose a different number of units from someone else's?
Because you probably mixed your vials differently. 250 mcg is 10 units from a vial mixed at 2,500 mcg per mL, and 25 units from one mixed at 1,000 mcg per mL. Same dose, different volumes. Anyone comparing unit numbers without comparing concentrations is comparing the wrong thing.
Can the calculator handle a vial with two compounds in it?
Yes, that is what the blend mode below is for. Put in each compound and its amount, the water you added to the shared vial, and a dose for one compound. You get the draw, plus what that same draw delivers of every other compound in the vial.
Arithmetic only
This calculator does maths on the numbers you enter. It works out concentration, draw volume and syringe units from the vial amount and water volume you give it. Nothing more.
It does not recommend amounts, schedules or products, and it does not know what is in your vial. It uses the amount printed on the label. If the label and the actual contents differ, the result differs too. For medical questions, talk to a clinician.
How the maths works, and where the facts on this site come from: Methodology and sources.