Free for everyone
Free peptide calculators that just work.
Reconstitution math, mcg/mg/IU dose conversion, and half-life modelling — three calculators that run in your browser, keep every input in the URL, and never ask you to sign in. Behind them sits a referenced library of 45 peptide profiles and 11 operations guides.
Free peptide calculators
Browse all peptide tools →Three tools cover the arithmetic that peptide protocols actually require: turning a vial and a volume of bacteriostatic water into a syringe mark, moving a dose between mcg, mg and IU, and seeing what a half-life does to plasma concentration over a dosing cadence. Each one has per-peptide variants pre-filled with the ratios that compound is usually reconstituted at.
Reconstitution
Calculator — exact units.
Vial mg + bacteriostatic water + target dose → the exact draw on a U-100, U-50, or U-30 insulin syringe. Every input lives in the URL, so a calculation is one link away.
- U-100, U-50, and U-30 insulin syringe support
- 40+ peptide presets — Tirzepatide, Semaglutide, BPC-157, CJC-1295…
- Shareable URLs — every input lives in the link
How peptide dosing maths works
Every number these calculators produce comes from two divisions and one conversion. If you understand those, you can check any result by hand — which is the point. Nothing below is a dosing recommendation; it is the arithmetic that sits underneath whatever dose a clinician has set.
How do you calculate peptide reconstitution?
Divide the vial strength by the volume of bacteriostatic water you add to get the concentration, then divide the target dose by that concentration to get the injection volume. A 10 mg vial reconstituted with 2 ml of bacteriostatic water is 5 mg/ml. A 2.5 mg dose from that vial is 0.5 ml — 50 units on a U-100 insulin syringe — and the vial holds four such doses. The reconstitution calculator does both divisions and draws the syringe at the resulting mark, so you can compare it against the barrel in your hand before you draw.
How many units is a dose on a U-100 insulin syringe?
On a U-100 insulin syringe 100 units is 1 ml, so units are simply millilitres multiplied by 100. U-50 syringes hold 0.5 ml and U-30 syringes hold 0.3 ml, but a unit means the same volume on all three barrels — there are just fewer of them. That is why a 0.5 ml draw reads as 50 units on a U-100, fills a U-50 completely, and cannot be drawn on a U-30 at all. The insulin syringe units guide walks through each barrel with the scales side by side.
How do you convert mcg, mg and IU?
Micrograms to milligrams is a factor of 1,000: 250 mcg is 0.25 mg. International units are not a mass at all — they measure potency, and the mass a unit corresponds to is specific to the compound. Somatropin is conventionally 3 IU per mg, so 1 IU is about 0.333 mg; human chorionic gonadotropin runs closer to 9,000 IU per mg. Applying one compound's ratio to another is a two-orders-of-magnitude error, which is why the dose converter holds a separate ratio per compound and ships a dedicated HGH IU converter.
What does a peptide half-life mean for dosing frequency?
A half-life is the time plasma concentration takes to fall by half. After roughly four to five half-lives a compound is functionally cleared. Dose more often than that and concentrations accumulate until intake and clearance balance — steady state. A compound with a 3-day half-life dosed every other day reaches steady state in about two weeks and settles at a peak-to-trough ratio near 1.8×, which is why long-half-life compounds tolerate weekly dosing and short ones usually do not. The half-life visualiser plots that curve for any half-life and cadence, and peptide half-lives explained covers the pharmacokinetics in plain language.
| Vial | Bacteriostatic water | Concentration | 250 mcg dose | 1 mg dose |
|---|---|---|---|---|
| 2 mg | 2 ml | 1 mg/ml | 25 units | 100 units |
| 5 mg | 2 ml | 2.5 mg/ml | 10 units | 40 units |
| 5 mg | 2.5 ml | 2 mg/ml | 12.5 units | 50 units |
| 10 mg | 2 ml | 5 mg/ml | 5 units | 20 units |
| 10 mg | 3 ml | 3.33 mg/ml | 7.5 units | 30 units |
| 15 mg | 3 ml | 5 mg/ml | 5 units | 20 units |
Concentration = vial strength ÷ water volume. Units on a U-100 = (dose ÷ concentration) × 100. Full walkthrough in how to reconstitute peptides.
Peptide reference library
All 45 peptide profiles →Forty-five profiles, each covering mechanism, commonly reported dose ranges, half-life, side-effect reports, storage, regulatory status, the stacks that compound appears in, and the primary sources we used. Where a peptide is injectable it links straight to its own pre-filled reconstitution calculator; where clearance matters it links to its half-life profile.
Operations guides
All 11 operations guides →The pillar guides cover the practical layer that biochemistry references skip: mixing, measuring, storing, travelling, and reading a certificate of analysis. They are the pages to read before you ever open a calculator.
Also in the library: what a peptide certificate of analysis shows, the red flags on a fake COA, how purity is verified, and travelling with peptides.
Peptide stacks
All 10 stack guides →Ten editorial write-ups of combinations that appear together in the literature and in user protocols — what each compound contributes, the cadence people report running, and the interactions worth watching. Each stack links to both constituent profiles and both reconstitution calculators.
Compare and shortlist
All peptide comparisons →Fourteen head-to-head breakdowns put two compounds in the same table — mechanism, half-life, dose range, evidence base and regulatory status — so the difference is legible rather than inferred. The goal-based shortlists do the opposite job: they start from what someone is trying to do and name the compounds the literature actually discusses for it.
If you are choosing software rather than a compound, the Peptide Protocol vs PeptIQ comparison and the spreadsheet-versus-app write-up are the honest versions, including what the app does not do.
From the journal
Read the peptide journal →Short pieces on the specific problems people hit mid-protocol — a vial that went cloudy, a dose that was missed, a certificate of analysis that says 98% and does not mean what it appears to.
Common questions about these tools
Are these peptide calculators free?
Yes — all three tools are free, need no account, and show no ads. They run entirely in your browser, which is also why every calculation is shareable: the reconstitution calculator keeps its inputs in the URL, so a link reproduces the exact result on someone else's screen.
Do you store what I type into the calculators?
No. The maths runs client-side and nothing is sent to a server, so there is no calculation history to store, sell, or leak. The only data that leaves your browser is the ordinary request for the page itself.
Which insulin syringe should I use for a peptide dose?
That is a question for the clinician or pharmacist supervising your treatment, not a calculator. Mechanically, the constraint is simple: the barrel has to be able to hold the volume. A 0.5 ml draw needs a U-100 or U-50 barrel because a U-30 syringe only holds 0.3 ml in total.
Why does the same dose show different unit counts on different pages?
Because unit count depends on concentration, not on the dose alone. The same 250 mcg dose is 25 units from a 2 mg vial reconstituted with 2 ml, and 5 units from a 10 mg vial reconstituted with 2 ml. Change the water volume and the unit count changes with it — which is exactly the mistake the calculator exists to prevent.
Is anything on this site medical advice?
No. peptide-calc.app is an educational reference and a set of arithmetic tools. Many peptides are prescription-only or restricted where you live, several are research chemicals with no human-use approval, and none of the pages here recommend that you take anything. Decisions about treatment belong with a licensed healthcare professional.
How this reference is written
peptide-calc.app is the free tools and reference companion to Peptide Protocol, an iPhone app for tracking peptide protocols. The pages here are written and maintained by the Peptide Protocol editorial team, reviewed against our medical review process, and sourced to drug labels, ClinicalTrials.gov records and PubMed-indexed literature wherever a factual claim is made. Where evidence for a compound is thin — which is true of most research peptides — the page says so instead of filling the gap.
Our editorial policy sets out how sources are tiered and what we refuse to publish; the corrections policy covers what happens when we get something wrong. The regulatory overview tracks approval and scheduling status, which for compounded GLP-1 agonists in particular has changed several times since 2023. There is more about who we are on the about page.
Last updated .
Track your protocol on iPhone.
These web tools handle the math. The iPhone app handles the routine — schedules, reminders, rotation, inventory, and insights, all on-device. Free.
More about the app at peptide-protocol.app.