Peptide Calculator
Mix the vial, draw the dose, plan the refill. Enter the vial strength, the bacteriostatic water you are adding, and the dose you want, and this calculator returns the concentration in mg/mL, the exact units to draw on a U-100 or U-40 insulin syringe, and how many doses the vial holds.
The short answer
Concentration is vial milligrams divided by milliliters of bacteriostatic water. Divide your dose by that concentration to get the draw volume in mL, then multiply by 100 for units on a U-100 syringe. A 5 mg vial mixed in 2 mL is 2.5 mg/mL, so a 250 mcg dose is 10 units.
This is a unit converter. It converts an amount you already have into volume and syringe units. It does not tell you what to take, and it is educational only — not medical advice. Confirm every amount with your clinician and your product label.
Example mixes to try the converter
Examples only — not recommended amounts. These fill in a vial size and diluent volume only — never an amount to inject. Enter the dose your clinician gave you yourself.
Calculator inputs
Total compound in the vial.
Volume of bacteriostatic water you reconstitute with.
Enter your target dose as a number.
U-100 = 100 units per mL (standard). U-40 = 40 units per mL.
- Enter your target dose as a number.
Save this mix to your protocol
Keep the concentration, dose, and mix date attached to the vial, and get reminded before you run out.
Save to DoseRoutineFree — the tool above stays free with or without an account.
How to read the result
The concentration line is the number that matters most, because it is the only one that changes when you mix a vial differently. Two people can inject the same 500 mcg dose and draw wildly different amounts on the syringe purely because one used 1 mL of bacteriostatic water and the other used 3 mL. Once you know the mg/mL figure, the syringe reading is fixed for as long as that vial lasts.
The units figure assumes a U-100 insulin syringe unless you switch the toggle. On a U-100 barrel, 100 units is exactly 1 mL, so every unit is 0.01 mL. U-40 syringes are still sold for veterinary insulin and are marked differently; drawing a U-100 number on a U-40 barrel delivers roughly two and a half times the intended volume, so check the barrel before you draw anything.
Doses per vial is a planning number rather than a promise. Syringe dead space quietly swallows a fraction of every draw, and a reconstituted vial has a beyond-use date measured in weeks, not months. Treat the figure as an upper bound and order the next vial before the last few doses.
Choosing your diluent volume
There is no single correct amount of bacteriostatic water. The peptide is the same regardless; the water only decides how easy the syringe is to read. Aim for a mix where your normal dose lands somewhere between 10 and 30 units. Below 10 units the markings are cramped and a small misread is a large percentage error; above 40 units you burn through volume quickly and may not fit larger doses in one draw.
If you dose more than one amount out of the same vial — a titration schedule, for instance — pick the diluent volume that keeps your largest planned dose under 100 units and your smallest above 8. Run both ends through the calculator before you add any water, because you cannot undo a mix.
Recording the mix
Write the date and the diluent volume directly on the vial the moment you reconstitute it. Almost every dosing error we hear about starts with a vial that was mixed one way and calculated another way a week later. Storing the protocol in DoseRoutine keeps the concentration, the dose, and the schedule attached to each other, and the vial tracker counts down remaining doses as you log them.
Frequently asked questions
What does a peptide calculator actually calculate?
Three things in sequence. Concentration is vial strength divided by the bacteriostatic water you add, in mg/mL. Draw volume is your dose divided by that concentration. Syringe units are the draw volume times 100 on a U-100 insulin syringe, or times 40 on a U-40. Everything else — doses per vial, days of supply — comes from those numbers.
How long will one vial last me?
Divide the vial strength by your per-injection dose to get the number of doses, then divide by how many injections you take per week to get weeks of supply. A 10 mg vial dosed at 500 mcg gives 20 doses, which is a little under three weeks at daily dosing or ten weeks at twice weekly — before you account for syringe dead space and the beyond-use date.
How much bacteriostatic water should I add to a vial?
Pick the volume that puts your usual dose between roughly 10 and 30 units on the syringe, because that band is the easiest to read without squinting. Adding more water does not weaken the peptide; it only spreads the same milligrams across more volume, which makes small doses easier to measure accurately.
Does the number of units change if I add more water?
Yes, and this is the single most common source of accidental double doses. Halving the water doubles the concentration, so the same milligram dose becomes half as many units. Write the diluent volume on the vial label the moment you reconstitute, and recalculate any time you mix a vial differently.
Can I use this calculator for semaglutide or tirzepatide?
The arithmetic is identical for any lyophilized peptide sold by weight in milligrams. It does not apply to prescription pens, which are pre-filled and dose-marked by the manufacturer — follow the pen's own markings and your prescriber's instructions rather than converting anything yourself.
What if my result is more than 100 units?
A draw above 100 units will not fit in one U-100 syringe, which usually means the vial was reconstituted with too much water for that dose. Mix the next vial with less diluent rather than taking two injections, and re-check that you have not mixed micrograms and milligrams in the same calculation.
Do I need to track the results anywhere?
You should record the mix date, diluent volume, and dose per injection somewhere you will see again, because the beyond-use date and the units figure both depend on them. Saving the result to a DoseRoutine protocol keeps the concentration attached to the vial and reminds you when the vial is near its end.
Related calculators and guides
More DoseRoutine calculators and side-by-side comparisons.
How we handle safety and your data
- DoseRoutine is a tracking and reference tool. It does not diagnose, prescribe, or replace your doctor or pharmacist.
- Interaction results are informational flags to discuss with a clinician — not clearances to combine anything.
- Dose calculators do the arithmetic you enter. They don't decide what you should take, or how much.
Read the medical disclaimer, editorial policy and how we source content.
Does DoseRoutine give medical advice?
No. DoseRoutine compiles publicly available reference information from sources such as NIH/MedlinePlus, FDA labeling, Mayo Clinic and PubChem, and shows you where interactions have been documented. It does not diagnose, prescribe or replace a clinician or pharmacist.
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Your stack, doses, labs and notes are yours. Data is stored in encrypted managed databases with row-level access controls, so only your account can read your records.
Do you sell my data or share it with advertisers?
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Can I delete my account and everything in it?
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Where does the interaction and compound data come from?
Interaction entries are compiled from public pharmacology and clinical literature, drug labeling and NIH resources, with PubMed IDs or DOI links attached where a specific study supports the entry. Every reference page links its sources so you can read the original.
Who builds DoseRoutine?
DoseRoutine is an independently built product, made by someone tracking their own peptide, hormone and supplement routine. It isn't funded by supplement brands or clinics, and no compound page is sponsored.
More detail in our privacy policy and full FAQ.