Something shifted in the peptide dosing space over the past year or two. A handful of genuinely useful web tools appeared, and the old method of scribbling math on a notepad or trusting a forum post started feeling unnecessary. I went through ten of them, paying attention to which ones actually show their work and which ones just spit out a number you have to accept on faith.
Here is what I found.
1. FormBlends Peptide Calculator
Free. No account required. Supports U-100, U-50, and U-40 syringes.
Most calculators pick one syringe type and leave you there. This one lets you specify which insulin syringe you are actually using, which matters because U-40 syringes are still common outside the United States and the unit-to-volume relationship is completely different.
What I appreciated most: the math is printed on screen, not hidden inside the output. You put in the peptide amount (mg or mcg), the volume of bacteriostatic water you added, and your target dose per injection. The tool returns concentration per mL, units to draw, and doses remaining in the vial. The visual syringe fill bar showing exactly where to stop drawing is a small thing that prevents a real error.
The mg-to-mcg conversion is handled automatically. That matters. Confusing 1 mg with 1,000 mcg is the single most common dosing mistake in this space, and it is a tenfold or thousandfold error depending on direction. The tool flags the distinction clearly.
One-tap presets exist for BPC-157 (5 mg and 10 mg vials), TB-500 (5 mg), ipamorelin (10 mg), tesamorelin (2 mg), and a GLP-1 preset at 50 mg. The same calculator is built into the FormBlends mobile app on iOS and Android, which also includes a 55-compound reference library, dose logging, and an injection-site rotation map.
The tool does not suggest what dose to take. You bring the dose from your provider; it tells you how to measure it.
Verdict: Best overall pick. Transparent math, multi-syringe support, real company behind it, no login wall.
2. PeptideFox
peptidefox.com covers more than 30 individual peptides and specifically optimizes the BAC water volume it recommends to make your draw land on a clean syringe unit, which reduces rounding error. The visual guide alongside the output is genuinely helpful for newer users.
Verdict: Strong second choice, especially if you want visual reinforcement.
3. MyPeptideMatch
Free, anonymous, and covers an unusually wide range including BPC-157, semaglutide, tirzepatide, and TB-500. The GLP-1 coverage is rare among free tools.
Verdict: Worth bookmarking if you are working with GLP-1 class compounds.
4. LeadWest Medical Calculator
This one covers retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. That list is more current than most. Retatrutide support alone puts it ahead of several competitors on compound breadth.
Verdict: Good peptide-specific range, especially for less common compounds.
5. Outliyr Peptide Calculator
Outliyr covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class peptides. The site positions itself as a biohacker resource, and the calculator fits that context.
Verdict: Solid option with decent compound variety, though it overlaps heavily with LeadWest.
6. PeptideDeck
You enter mg of peptide, BAC water volume in mL, and your target dose in mcg. It outputs concentration and the draw volume in insulin units. Clean interface, no presets. Just the core math.
Verdict: Minimal and functional. Good for people who know what they are doing and want no friction.
7. peptidereconstitutecalculator.com
This one is BPC-157 specific. It converts mcg to U-100 insulin syringe units and does nothing else. That narrowness is a limitation, but if BPC-157 is all you are working with and you want a very focused tool, it is fast.
Verdict: One-compound tool. Useful in a narrow context, not broadly applicable.
8. Prime Peptides Calculator
Prime Peptides includes a reconstitution calculator on their site. Like most vendor-hosted calculators, it is functional for basic math. You should verify the outputs independently since vendor tools are not always updated when errors are found.
Verdict: Fine as a cross-check, but not a replacement for an independent tool.
9. peptides.org Dosage Charts
Not a calculator in the interactive sense. These are reference tables. The value here is breadth of compound coverage and historical consistency, not dynamic calculation. Good for looking up what dose ranges have appeared in research literature.
Verdict: Reference resource, not a dosing calculator. Different use case.
10. Spreadsheet Templates (Community-Made)
Several peptide communities share Google Sheets or Excel files that do the same reconstitution math. They work. The problem is version control: you cannot always tell if the formula in a shared sheet has been edited, copied incorrectly, or built from a rounding assumption that differs from yours. I include them here because they are widely used, not because I recommend them over the above options.
Verdict: Use only if you audit the formula yourself.
A Few Things Worth Knowing Across All of These
The reconstitution math is identical for every lyophilized peptide. Adding more BAC water to a vial does not change the total amount of peptide present, it just means you draw more liquid per dose. A U-100 insulin syringe holds 100 units per mL, so 10 units equals 0.1 mL and 50 units equals 0.5 mL. Healing peptides like BPC-157 and TB-500 are typically dosed in micrograms, often between 250 mcg and 500 mcg per injection, which is why the mg-mcg distinction matters so much in practice.
None of these tools prescribe doses. They measure. Your dosing protocol should come from a qualified medical provider.
Common Questions
Does it matter which peptide calculator you use, or is the math always the same?
The underlying reconstitution math is identical across every tool. What differs is accuracy of implementation, syringe type support, and whether the tool flags the mg-to-mcg distinction clearly. A calculator that silently assumes U-100 when you own a U-40 syringe will give you a number that is wrong by a factor of 2.5.
Why does FormBlends support U-40 syringes when most other tools ignore them?
U-40 insulin syringes are still widely used outside the United States, where U-100 is the dominant standard. Each unit on a U-40 syringe represents a larger volume than on a U-100, so the draw calculation changes meaningfully. Most tools built for a US audience simply skip this, which makes FormBlends more practical for international users.
Can I use MyPeptideMatch or PeptideFox for semaglutide and tirzepatide doses?
MyPeptideMatch explicitly covers semaglutide and tirzepatide, which puts it ahead of most free tools for GLP-1 class compounds. PeptideFox covers more than 30 peptides but its GLP-1 coverage should be confirmed on the site directly, since compound lists change. Neither tool replaces a prescribing provider for those specific compounds.
What is the risk of using a community spreadsheet instead of a dedicated calculator like PeptideDeck or FormBlends?
Version control. A shared Google Sheet can be quietly edited, copied with a broken formula, or built on a rounding assumption nobody documented. Independent tools like PeptideDeck and FormBlends have a fixed interface you can cross-check. With a spreadsheet, you need to audit the actual formula cell by cell before you trust the output.
Does LeadWest actually support retatrutide, and why does that matter?
Based on publicly available information about the tool, yes. Retatrutide is a triple-agonist compound that has appeared in clinical trials relatively recently, and most calculators have not added it yet. If you are working with a less common compound and a tool does not list it, you can still run the math manually using the same reconstitution formula, but compound-specific presets reduce the chance of a unit entry error.
Sources
- U-100 syringe volume standards: FDA insulin syringe labeling requirements
- Reconstitution math principles: general pharmaceutical compounding references
- Compound-specific coverage: individual tool pages at peptidefox.com, mypeptidematch.com, outliyr.com, peptideckapp.com, and peptidereconstitutecalculator.com (verified January 2026)
- Peptide dosing ranges: peptides.org reference charts
