Something shifted in early 2025. GLP-1 peptides went mainstream, telehealth prescriptions for tirzepatide and semaglutide exploded, and suddenly a lot of people who had never touched a vial were staring at a lyophilized powder and a bottle of bacteriostatic water with no idea what to do next. The reconstitution math itself is not complicated. But the mg-to-mcg conversion is, and mixing them up by a factor of 1,000 is the single most common dosing error in this space. A good calculator prevents that. A bad one just does arithmetic and leaves you guessing.
I tested seven tools. Here is what I found.
Quick Comparison
| Tool | Peptide Presets | Syringe Types | Shows Math | App / Web | Free |
| FormBlends Peptide Calculator | BPC-157, TB-500, ipamorelin, tesamorelin, GLP-1 class, more | U-100, U-50, U-40 | Yes | Both | Yes |
| PeptideFox | 30+ peptides | U-100 | Partial | Web only | Yes |
| PeptideDeck | Any (manual entry) | U-100 | Yes | Web only | Yes |
| MyPeptideMatch | BPC-157, sema, tirz, TB-500 | U-100 | No | Web only | Yes |
| LeadWest Medical | BPC-157, TB-500, ipamorelin, CJC-1295, retatrutide, more | U-100 | No | Web only | Yes |
| Outliyr | BPC-157, TB-500, ipamorelin, GLP-1 class, GHK-Cu | U-100 | No | Web only | Yes |
| peptidereconstitutecalculator.com | BPC-157 only | U-100 | No | Web only | Yes |
1. FormBlends Peptide Calculator
The single detail that sets this apart from every other tool on this list: the math is printed on screen, step by step, so you can actually check what the calculator did rather than trust a black box.
That matters more than it sounds. Enter your vial size in mg, the mL of BAC water you added, and your target dose in mcg. The tool outputs concentration per mL, the exact units to draw, and a visual syringe fill bar showing where the plunger stops. It also handles U-50 and U-40 syringes, not just the standard U-100, which is relevant for anyone who has sourced a different syringe gauge and wondered whether the numbers still apply.
One-tap presets cover the most common vials: BPC-157 at 5 mg and 10 mg, TB-500 at 5 mg, ipamorelin at 10 mg, tesamorelin at 2 mg, and a 50 mg GLP-1 option. The mg/mcg conversion happens automatically, with a clear note explaining why that conversion exists and where the dangerous confusion comes from. It does not guess your dose. You supply the dose from your provider; the tool tells you how to measure it.
The same calculator is baked into a companion mobile app on iOS and Android, which adds a 55-compound reference library, dose logging, and an injection-site rotation tracker. The web version needs no account. The app needs no subscription. FormBlends is a 503A compounding pharmacy, so there is an actual business behind the tool rather than an orphaned webpage from 2019.
2. PeptideFox
PeptideFox supports more than 30 peptides. More importantly, it focuses on BAC water volume optimization, helping you find a water volume that produces clean, whole-unit draws on a U-100 syringe. Fractional units are where measurement errors happen. The site includes a visual guide alongside the numbers. No app, no login, no cost.
3. PeptideDeck
Straightforward and honest about what it is. You enter the vial’s mg content, how many mL of water you added, and the mcg dose you want. It returns concentration, draw volume, and insulin units. No presets, which means it works for any peptide. The math output is visible. Good backup tool when you have something outside the common preset lists.
4. MyPeptideMatch
Free, anonymous, and specifically covers the GLP-1 injectables alongside healing peptides. If you are working with semaglutide or tirzepatide, most other tools do not list those by name. This one does. No math shown, but the inputs and outputs are clearly labeled.
See also: Why Branded Handbags Remain a Timeless Fashion Investment
5. LeadWest Medical
A clinical-facing calculator that covers several peptides including retatrutide, which almost none of the other tools mention. Clean interface. No explanation of the math, but the peptide list is broader than average, and it appears to be maintained by an actual medical practice rather than a hobbyist page.
6. Outliyr
Covers GHK-Cu in addition to the standard healing peptide lineup, which is uncommon. Outliyr is primarily a biohacking content site, and the calculator feels like one section of a larger resource rather than a standalone tool. Functional for the peptides it lists.
7. peptidereconstitutecalculator.com
BPC-157 only, U-100 only, mcg-to-units conversion. Extremely narrow scope. If that is the only thing you need and you want the simplest possible page, it works. For anything else, you will need a different tool.
The One Thing Every Tool Gets Right (and the One Thing Most Miss)
The underlying math is identical for every lyophilized peptide. Add more water and your concentration drops, so you draw more units to get the same dose. That is not a quirk of any specific compound. It is just dilution. Most of these tools explain that correctly.
What most miss is showing the arithmetic. When a tool hides its formula, you cannot catch a data-entry mistake. FormBlends shows the work. PeptideDeck shows the work. The rest just hand you a number.
Common Questions
Which of these calculators actually works for semaglutide and tirzepatide, not just research peptides?
MyPeptideMatch names semaglutide and tirzepatide explicitly in its preset list, which most tools skip entirely. FormBlends covers a 50 mg GLP-1 class option. LeadWest Medical also lists GLP-1 compounds. If you are working with a compounded GLP-1 vial, those three are the practical starting points.
Why does FormBlends show the math while most other tools just give you a number?
FormBlends is built by a 503A compounding pharmacy with a clear interest in preventing dosing errors. Showing the step-by-step arithmetic lets you catch your own data-entry mistakes before you draw. PeptideDeck does the same thing. The tools that hide the formula are not wrong, but you have no way to verify them if something looks off.
If I have a U-40 or U-50 syringe instead of a standard U-100, which tool can I actually use?
FormBlends is the only tool on this list that handles U-40 and U-50 syringes alongside U-100. Every other tool assumes U-100. Using a U-40 syringe with U-100 calculations produces a significant overdose, so this is not a minor distinction if you have sourced a non-standard syringe.
Does PeptideFox cover retatrutide, or do I need a different tool for that?
PeptideFox does not list retatrutide among its presets. LeadWest Medical is the only tool reviewed here that specifically names retatrutide. PeptideDeck can handle it through manual entry since it accepts any vial size and dose without requiring a preset, making it a workable fallback for less common compounds.
Can any of these tools substitute for a prescription or medical guidance on what dose to take?
No. Every tool here is a measurement aid, not a dosing authority. You supply the target dose, typically from a prescribing provider, and the calculator tells you how many units to draw. None of them recommend doses, and using them without a confirmed target dose from a qualified clinician is outside what these tools are designed for.
Sources
- U-100 syringe volume standard: FDA insulin syringe labeling guidance
- BPC-157 and TB-500 common dosing ranges: published research summaries at peptides.org
- Syringe unit conventions (U-40, U-50, U-100): BD Medical insulin delivery resources
- GLP-1 peptide calculator coverage: MyPeptideMatch, LeadWest Medical public tool pages
- PeptideFox feature list: peptidefox.com public tool description (verified 2025)
