Every peptide calculator on the internet does the same division: milligrams in the vial ÷ milliliters of bacteriostatic water = concentration. What separates a good one from a bad one is whether it shows that math, whether it handles mg/mcg/units without tripping, and whether it makes you wade through popups, email gates, or a store trying to sell you something before you get an answer. We built ours to clear that bar, and this page is the honest tour of what exists.
What a peptide calculator actually needs to do
Three inputs: the amount of peptide in the vial, the volume of water you add, and the amount you want to measure out. One output: the volume (or insulin-syringe units) that corresponds. Anything beyond that — compound presets, common vial sizes, a visual syringe — is convenience, not correctness. The failure mode that matters is unit confusion: a calculator that silently mixes up mg and mcg is off by 1,000×. That's why every calculator we publish states its formula on the page, in plain text, so the result can be checked by hand.
The compound-specific calculators (all free)
A generic calculator works for everything, but compound-specific pages preload the vial sizes that compound actually ships in — which is where most real-world mistakes start. The most-used ones on this site:
- Semaglutide dosage calculator — the most-searched peptide calculator on the site, preloaded with 5 mg and 10 mg research vials.
- Tirzepatide calculator — 10/15/30 mg vials.
- Retatrutide calculator — 10/15/30 mg vials.
- BPC-157 calculator and TB-500 — the recovery-research pair.
- CJC-1295 / Ipamorelin blend calculator — handles the blend ratio for you.
- PT-141, GHK-Cu, NAD+, MOTS-C — and 20 more from the calculator hub.
There's also the general-purpose reconstitution calculator on the calculator hub for anything not listed, and a Spanish-language calculadora de péptidos.
What about other calculators?
Plenty of vendor sites host a calculator next to their checkout button. The math is usually fine — division is division — but understand the incentive: those pages exist to sell vials, and some quietly preload their own product sizes or wrap the tool in tracking. A calculator hosted by a store isn't neutral ground. Ours sit on an independent site that sells nothing, and the same page links the bacteriostatic water answer hub for the questions the calculator can't answer — how long reconstituted material lasts, how to store it, what bac water actually is.
The checklist for judging any calculator
Wherever you do the math, hold the tool to this: it shows the formula; it labels every unit explicitly; it doesn't require an email; it works without JavaScript errors on a phone; and the site hosting it isn't using it as a funnel to an unverified store. If a calculator fails two of those, do the division yourself — vial mg ÷ mL added = mg/mL, and from there it's arithmetic.
For research use only. This article is educational and makes no health, dosing, or usage claims of any kind.