12 Reconstitution Calculators I Actually Trust for Getting Peptide Doses Right
Something shifted in the last year or two. When I started tracking peptide dosing tools, most of them were throwaway single-page sites with no clear author, no syringe-type support, and math you just had to take on faith. Now there are proper tools, app-integrated ones, and a few that show their work. The gap between the good ones and the junk has gotten wider. Here is what I actually use and recommend, ranked by how much I trust them day-to-day.
1. FormBlends Peptide Calculator
Free. No account. That alone puts it ahead of half the tools on this list.
You enter three numbers: the peptide amount in the vial (mg or mcg), the volume of bacteriostatic water you added (mL), and your target dose per injection. It outputs concentration per mL, the exact units to draw on your insulin syringe, and a vial dose count. What makes it genuinely useful is that it supports U-100, U-50, and U-40 syringes, handles mg-to-mcg conversion automatically (1 mg equals 1000 mcg, a mismatch that causes dangerous 1000x errors), and shows the underlying math so you can verify each step yourself rather than trusting a black box.
The visual syringe fill bar is a small thing that matters a lot when you are learning. You can see exactly where on the barrel your dose sits. One-tap presets cover BPC-157 at 5 mg and 10 mg, TB-500 5 mg, ipamorelin 10 mg, tesamorelin 2 mg, and a 50 mg GLP-1 option. It also explains clearly why adding more BAC water changes the units you draw without changing the total dose delivered, which trips up a lot of first-timers.
The web tool is also built into the FormBlends app (iOS and Android), which adds a 55-compound reference library, dose logging, and an injection-site rotation map. It is backed by a real 503A compounding pharmacy rather than an anonymous domain, which matters for accountability. It does not recommend doses at all. You bring the dose, it tells you how to measure it.
2. PeptideFox
peptidefox.com covers 30-plus peptides and does something smart: it optimizes BAC water volume for clean unit draws on a U-100 syringe, so you are not left pulling 0.37 mL and guessing. The visual reconstitution guide is genuinely helpful for beginners.
3. PeptideDeck
Simple three-field interface: enter mg in the vial, BAC water added, and target dose in mcg. Outputs concentration and the exact draw volume in insulin units. No extras, no library. Fast.
4. MyPeptideMatch
Covers BPC-157, TB-500, semaglutide, tirzepatide, and several other injectables. Free. The GLP-1 coverage is rarer than you would think among dedicated peptide tools, which makes this one worth bookmarking if you are working with that class.
5. LeadWest Medical Calculator
Handles retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. Medical practice context means the framing skews clinical. Good for cross-referencing your math.
6. Outliyr Peptide Dosing Tool
Covers a similar compound list to LeadWest, including BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class peptides. Outliyr publishes a lot of longevity-adjacent content, so the calculator sits inside a broader reference context.
7. peptidereconstitutecalculator.com
BPC-157-focused, nothing more. Takes a mcg dose and translates it into the corresponding graduation on a U-100 syringe. Narrow scope, but it does that one job clearly. Good for double-checking a BPC-157 draw.
8. Prime Peptides Calculator
Part of the Prime Peptides vendor site. Does reconstitution math for their catalog. Useful if you are working with their products specifically. I would still cross-check any vendor-site tool against an independent one.
9. peptides.org Dosage Charts
Static reference tables rather than an entry-and-output tool. I use these as a sanity check, not a primary tool. The data is generally conservative and well-sourced.
10. Manual Calculation (U-100 Reference)
Not a website, but worth including. A U-100 syringe holds 100 units per 1 mL. 50 units equals 0.5 mL, 10 units equals 0.1 mL. If you dissolve 5 mg (5000 mcg) of BPC-157 in 2 mL of BAC water, concentration is 2500 mcg/mL. A 500 mcg dose is 0.2 mL or 20 units on a U-100. That math works for any lyophilized peptide. Knowing it means no tool can fool you.
11. Spreadsheet Templates (Community-Built)
r/Peptides and a few Discord servers have shared Google Sheets that replicate the same formula. No visual polish, but the logic is auditable line by line. Worth having offline.
12. Your Prescribing Provider’s Guidance
Last on this list, first in practice. Any calculator, including the best ones above, is a measurement aid. None of them know your weight, your health history, or your protocol. A qualified provider sets the dose. You use a calculator to measure it accurately.
A Quick Note on Using These Tools
Reconstitution calculators do math. They do not screen for interactions, contraindications, or whether a particular peptide is right for your situation. Some of the tools above are anonymous pages with no disclosed author. Verify the math yourself using the U-100 formula before you trust any result. When in doubt, ask a licensed clinician.
Common Questions
Why does changing the BAC water volume alter how many units I draw, even though the dose stays the same?
Because concentration changes when you add more or less liquid to the vial. The total peptide mass is fixed. More water means lower concentration, so the same dose occupies more volume in the syringe. FormBlends explains this step explicitly, which is one reason it is worth using while you are still building the intuition.
Does it matter which reconstitution calculator I use for GLP-1 peptides like semaglutide or tirzepatide, versus something like BPC-157?
The underlying math is identical. What differs is compound coverage. MyPeptideMatch and Outliyr both include semaglutide and tirzepatide, while peptidereconstitutecalculator.com is BPC-157 only. For GLP-1 class peptides, pick a tool that lists those compounds by name so you can confirm the default units and vial sizes match what you actually have.
Is it safe to rely on a vendor-site calculator like the one from Prime Peptides?
The math on a vendor calculator is not inherently wrong, but there is an obvious conflict of interest in a seller providing the tool you use to measure their product. Cross-check any vendor-site result against an independent calculator such as FormBlends or PeptideDeck before drawing a dose. Two minutes of verification is a reasonable habit.
What is the single most common arithmetic mistake people make when using these tools for the first time?
Mixing up mg and mcg. One milligram equals 1000 micrograms. Entering a dose in mg when the tool expects mcg, or vice versa, produces a 1000-fold error in the draw volume. FormBlends converts automatically and flags the unit. Most other tools on this list require you to enter the correct unit yourself, so double-check which one the field is asking for before you calculate.
Does the FormBlends calculator work for peptides not in its preset list, or is it limited to the named compounds?
It works for any lyophilized peptide. The presets for BPC-157, TB-500, ipamorelin, and others are shortcuts, not limits. You can type in any vial size, any BAC water volume, and any target dose in mg or mcg, and the calculator runs the same concentration math regardless of which compound is in the vial.
Sources
- U-100 insulin syringe standard: USP and FDA labeling conventions for insulin syringes
- peptidefox.com, peptidefox, public tool documentation
- peptidereconstitutecalculator.com, public tool
- peptides.org, public dosage reference charts
- Prime Peptides calculator, public vendor tool
- FormBlends app, public App Store/Google Play listing and web tool
