Something shifted in 2025 and into 2026: the number of free, browser-based tools for peptide dosing math went from a handful of scattered Reddit spreadsheets to a small but real ecosystem of dedicated calculators. GLP-1 interest drove a lot of that growth. So did the expanding use of healing peptides like BPC-157 and TB-500 outside clinical settings. The tools below are not all equal, and some are one-page hobby projects with no named author. That matters. Here is what each one actually does.
For People Starting With Any Lyophilized Peptide
1. FormBlends Peptide Calculator
The single most useful thing about this tool is that it shows the math instead of hiding it behind a black-box output. You type in your vial size (mg or mcg), the volume of bacteriostatic water you added, and your target dose per injection. What comes back is the concentration per mL, the exact insulin units to draw, and a count of how many doses remain in the vial. A visual syringe bar marks where your plunger stops. That last part sounds minor until you are squinting at tiny tick marks at 6 a.m.
It handles U-100, U-50, and U-40 syringes, which matters because U-40 syringes still circulate in some countries and the math is different. The mg-to-mcg conversion (1 mg equals 1,000 mcg) happens automatically. Getting that wrong by a factor of 1,000 is genuinely the most common dangerous mistake in peptide self-administration. One-tap presets cover BPC-157 at 5 mg and 10 mg, TB-500 at 5 mg, ipamorelin at 10 mg, tesamorelin at 2 mg, and GLP-1 compounds at 50 mg. No account required. The same calculator lives inside the FormBlends mobile app (iOS and Android), which adds a 55-compound library, injection-site rotation tracking, and dose logging. FormBlends is a named telehealth company with a 503A compounding pharmacy affiliation, not an anonymous page.
2. PeptideDeck
Clean interface. Enter the vial size in mg, your BAC water volume in mL, and a target dose in mcg. It returns concentration and the draw volume in both mL and insulin units. Nothing more, nothing less. Good for people who want a fast answer without presets or explanations. No app.
For Visual Learners and Beginners
3. PeptideFox
This one supports more than 30 named peptides and does something the others mostly skip: it explains how your choice of BAC water volume affects the units you draw on the syringe. More water means more units per dose, but the dose itself stays the same. A lot of first-timers get confused by that. PeptideFox walks through it with a visual guide, which earns it a spot in this group.
4. peptidereconstitutecalculator.com
Narrow scope. It handles BPC-157 specifically and outputs mcg-to-units conversions assuming a U-100 syringe. Short learning curve. If BPC-157 is the only compound you are working with, this gets the job done without distraction. Do not expect multi-peptide support.
For GLP-1 and Weight-Loss Peptide Users
5. MyPeptideMatch
Free tool covering semaglutide, tirzepatide, BPC-157, and TB-500 among others. The GLP-1 coverage is what sets it apart from older calculators built purely around research peptides. No sign-up.
6. Outliyr
Covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and the GLP-1 class in one place. The page reads more like an editorial guide than a pure calculator. That is either a feature or noise depending on what you want from the session. Good for context alongside the math.
For Clinical or Research-Adjacent Users
7. LeadWest Medical
This one covers retatrutide, which very few free tools bother with. It also handles BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. LeadWest is a medical practice, not a software company, so the calculator exists as a patient resource rather than a standalone product. The list of supported compounds is longer than most.
Reference Charts Rather Than Interactive Calculators
8. peptides.org Dosage Charts
Static. No inputs, no outputs. What peptides.org offers is reference-grade dosage range data for a wide range of compounds. Use it to understand typical protocol ranges before you sit down with an actual calculator. Not a substitute for one.
9. Prime Peptides Calculator
A vendor-hosted tool. Prime Peptides is a peptide supplier, so the calculator exists inside a commercial context. The math it performs is the same reconstitution math every other tool uses because the reconstitution math is universal: concentration equals vial size divided by water volume, draw volume equals target dose divided by concentration. That said, vendor-hosted tools should be cross-checked, since there is an obvious interest in keeping customers comfortable enough to order again.
One Thing Every Calculator Above Assumes
A U-100 insulin syringe holds 100 units per mL. Full stop. So 10 units on the syringe barrel equals 0.1 mL, and 50 units equals 0.5 mL. Every piece of dosing math on this list is built on that relationship. If your syringe is U-40 or U-50, the unit markings mean different volumes, and you need a calculator that explicitly supports your syringe type. Most of these tools default to U-100 without saying so.
None of these tools prescribe a dose. They convert a dose you already have from a qualified provider into a measurement on a syringe. That distinction is not fine print. It is the entire point.
Common Questions
Does it matter which calculator you use if the reconstitution math is the same?
For the arithmetic itself, no. Every tool divides vial size by water volume to get concentration, then divides your target dose by that concentration. What differs is error prevention: tools like FormBlends show the step-by-step work and flag the mg-to-mcg conversion, which is where most dangerous mistakes happen. A bare-bones calculator won’t catch that.
Why does FormBlends list a 503A compounding pharmacy affiliation, and should that change how much you trust its calculator?
A 503A affiliation means FormBlends operates within a regulated compounding context, subject to FDA oversight on sterile preparations. It does not automatically make the calculator more accurate, since the math is universal, but it does mean the company has a legal identity and regulatory exposure, unlike anonymous one-page tools with no named author.
If I add more bacteriostatic water to my BPC-157 vial than the calculator assumed, do I need to redo the whole calculation?
Yes, immediately. The concentration changes the moment the water volume changes. Tools like PeptideFox and FormBlends let you re-enter the water volume and recalculate in seconds. Using the old unit draw with a new water volume is exactly the kind of error these calculators exist to prevent.
Does any tool on this list support retatrutide, and why is that compound harder to find in free calculators?
LeadWest Medical is the only tool in this list that explicitly covers retatrutide. It is a newer compound with limited public protocol data compared to semaglutide or BPC-157, so most hobby-built calculators have not added it. LeadWest’s calculator appears to exist primarily for its own patient population, which likely includes people prescribed retatrutide through the practice.
Can I use peptidereconstitutecalculator.com for TB-500 if I already know the BPC-157 math?
No. That site is scoped to BPC-157 specifically and assumes a U-100 syringe throughout. TB-500 is typically dosed in the 2.5 mg to 5 mg range per injection, which produces different unit draws than a standard BPC-157 protocol. Use a multi-peptide tool like FormBlends, PeptideFox, or LeadWest Medical for TB-500 instead.
Sources
- U-100 insulin syringe specifications: FDA guidance on insulin syringes and unit standardization
- BAC water reconstitution math: general pharmaceutical compounding references (anhydrous, unit-conversion basis)
- peptides.org: public dosage reference charts, accessed 2025-2026
- PeptideFox: peptidefox.com, public tool, verified 2025
- LeadWest Medical: public calculator page, verified 2025
- MyPeptideMatch: public tool, verified 2025
- Outliyr: public editorial calculator, verified 2025
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