The math behind peptide dosing has not changed. What has changed is the tooling. A few years ago, most beginners were doing reconstitution math on scratch paper or copying forum posts with obvious typos. In 2025 and into 2026, a small cluster of dedicated web calculators and apps finally filled that gap, and the quality spread between them is wider than you might expect.
This piece covers six tools, ranked by how useful they are to someone holding their first vial.
1. PeptideFox
The strongest general-purpose option available right now. PeptideFox supports over 30 named peptides and, more importantly, actually optimizes the bacteriostatic water volume you should add based on your target dose and syringe type. That detail matters. Most beginners pour in 2 mL by default, then wonder why they are drawing fractional units on a tiny insulin syringe. PeptideFox removes the guesswork on that step. The visual guide it includes is genuinely useful for people who have never handled a U-100 syringe before. Free, no signup, browser-based.
2. FormBlends Peptide Calculator
Best pick for someone who keeps confusing milligrams and micrograms, which, statistically, is most beginners.
The mg-vs-mcg error is the single most common mistake in peptide prep. It is a 1000x miscalculation. Someone meaning to dose 500 mcg ends up drawing for 500 mg and either wastes the vial or, worse, injects a dangerous amount. FormBlends built this tool specifically around preventing that conversion error. You enter your vial size in mg or mcg, the water volume you added, and your intended dose per injection. The calculator outputs concentration per mL, exact units to draw, and total doses remaining in the vial. It works for U-100, U-50, and U-40 syringes without switching modes.
Two things separate it from the anonymous calculator pages. First, the arithmetic is printed on screen, not hidden, so you can follow along and catch anything that looks off. Second, a visual syringe bar shows where the plunger should stop. For a first-timer, seeing the fill line drawn out is worth more than a plain number.
One-tap presets cover BPC-157 at both 5mg and 10mg vial sizes, TB-500 5mg, ipamorelin 10mg, tesamorelin 2mg, and GLP-1 compounds at 50mg. The same calculator lives inside the FormBlends mobile app (iOS and Android), which adds dose logging, an injection-site rotation map, and a 55-compound reference library. The web version requires no account. The company behind it operates a 503A compounding pharmacy, so there is an actual business entity with accountability here, not just an anonymous domain.
What it will not do: recommend a dose. You supply the number. The tool only tells you how to measure it accurately. That is the right design choice.
3. PeptideDeck
Minimal and fast. Enter the total mg in the vial, the mL of BAC water added, and the target dose in mcg. PeptideDeck returns the concentration and the draw volume in both mL and insulin syringe units. Nothing extra. If you already know your dose and just need the draw calculation confirmed quickly, this is the fastest path to that answer. No presets, no visual aids, but also no friction.
4. MyPeptideMatch
Covers a wider compound list than most, including semaglutide and tirzepatide alongside the more common healing peptides like BPC-157 and TB-500. GLP-1 class compounds are dosed differently (weekly, in mg) and most generic calculators do not handle them well. MyPeptideMatch does. Free, no account needed. Useful if you are specifically working with GLP-1 injectables and want a tool that acknowledges how those dosing schedules work in practice.
5. LeadWest Medical Calculator
A clinically-oriented page covering retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. The compound list skews toward what a peptide-prescribing physician might actually order. Good reference if your provider gave you a prescription and a vial and left the measurement math to you.
6. peptidereconstitutecalculator.com
BPC-157 only. Very narrow, but sometimes that focus is exactly what you need. Converts mcg to units on a U-100 syringe for BPC-157 specifically, and it does that one job clearly. If BPC-157 is the only peptide you are working with and you want the simplest possible tool, start here. Not the right choice once you add a second compound.
The One Piece of Math Worth Memorizing
A U-100 insulin syringe holds 1 mL across 100 units. That means 10 units equals 0.1 mL. Adding more bacteriostatic water to a vial does not change the total peptide inside it. It changes how many units you need to draw to get your dose. Every calculator on this list is doing the same division. The tools differ in clarity, breadth, and error-prevention, not in the underlying formula.
A Note on These Tools
None of the calculators listed here tell you what dose to take, and neither does this article. Peptide dosing decisions belong with a qualified prescriber. These tools measure accurately once you have a number from a provider. Getting the draw volume right matters, but it is the second step, not the first.
Common Questions
Does the amount of bacteriostatic water you add to a vial actually change your dose?
No, and this trips up a lot of first-timers. The total peptide in the vial stays fixed regardless of how much BAC water you add. More water means a more dilute solution, so you draw more units to hit the same dose. PeptideFox specifically optimizes the water volume for your syringe type to keep draw volumes readable.
Which of these calculators works for semaglutide or tirzepatide, and why do most fail at it?
MyPeptideMatch is the clearest choice for GLP-1 compounds. Most generic reconstitution tools assume daily mcg dosing and fall apart when the schedule shifts to weekly mg doses, which is standard for semaglutide and tirzepatide. FormBlends also includes a 50mg GLP-1 preset, making it a workable backup option.
If I only have BPC-157 and want the least complicated tool possible, which one should I open first?
Start with peptidereconstitutecalculator.com. It does one thing: converts your BPC-157 dose in mcg to units on a U-100 syringe. No compound list to scroll through, no extra inputs. Once you add a second peptide to your protocol, move to PeptideFox or FormBlends, which handle multiple compounds without switching tools.
What makes the FormBlends calculator safer for beginners than a plain unit-conversion page?
Two specific features. The calculator prints its arithmetic on screen so you can verify each step rather than trust a black-box output. It also draws a visual syringe fill line so you can see where the plunger stops, not just read a number. Both features directly address the mg-vs-mcg confusion that causes 1000x dosing errors.
Do any of these tools log doses or track injection sites over time, or are they all single-use calculators?
Most are single-use web tools with no memory between sessions. The FormBlends mobile app (iOS and Android) is the exception. It adds a dose log, an injection-site rotation map, and a 55-compound reference library on top of the same calculator the web version offers. Useful if you are managing a multi-week protocol and want a record.
Sources
- PeptideFox public tool documentation, peptidefox.com
- PeptideDeck interface, publicly accessible web tool
- MyPeptideMatch public tool, compound list verified
- LeadWest Medical calculator, compound list verified via public page
- U-100 syringe volume specification, standard insulin syringe labeling
- FormBlends mobile app listing, iOS/Android app stores
