Here is the honest truth about this category: most “peptide calculators” online are anonymous one-page tools with no company, no update history, and no explanation of the math they are running. That is fine for basic arithmetic, but when a U-100 syringe holds 100 units per mL and a single mg/mcg confusion can put you off by a factor of 1,000, “anonymous and unexplained” starts to feel like a problem. I have spent time sorting through what is actually out there. These twelve tools are worth bookmarking.
How I Evaluated These Tools
Recurring themes in peptide communities: people want to know units to draw on an insulin syringe, not just concentration in mg/mL. They want to handle the mg-to-mcg conversion safely. And they want to understand what happens when they change the amount of BAC water they add. The best tools address all three. The weakest ones skip at least one.
1. PeptideFox
The strongest all-around option I found. PeptideFox (peptidefox.com) covers more than 30 named peptides and does something most tools skip: it helps you optimize how much BAC water to add so your target dose lands on a clean, readable unit mark on the syringe. That is genuinely useful, not cosmetic. It also includes a visual guide. Free, specific, and clearly maintained.
2. FormBlends Peptide Calculator
Free, no sign-up required, and it shows the actual math rather than just spitting out a number. That transparency is what sets it apart from most anonymous pages.
You enter three things: the total peptide 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, and the total number of doses in the vial. A visual syringe fill bar shows where on the barrel your dose sits. One-tap presets cover common vials like BPC-157 at 5 mg and 10 mg, TB-500 at 5 mg, ipamorelin at 10 mg, tesamorelin at 2 mg, and a GLP-1 preset at 50 mg.
It defaults to U-100 but also supports U-50 and U-40 syringes, which matters if you are using a different barrel. The mg-vs-mcg conversion is handled automatically; the tool exists specifically because mixing those two up by a factor of 1,000 is the most common serious mistake in peptide dosing.
FormBlends is an actual telehealth and 503A pharmacy company, not an anonymous page, which gives the tool a bit more accountability than most in this category. The same calculator lives inside the FormBlends mobile app (iOS and Android), which adds a 55-compound library, dose logging, and an injection-site rotation map. The web version works fine on its own. It does not recommend a dose; you bring the dose your provider gave you, and it tells you how to measure it.
3. MyPeptideMatch
Free and notably up to date. It covers BPC-157, TB-500, semaglutide, tirzepatide, and other injectables including some GLP-1 class compounds that older tools ignore entirely. Good choice if you are working with any of the newer weight-management peptides.
4. LeadWest Medical Calculator
This one skews toward a clinical audience. It handles retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. The range of peptides is solid. Worth checking if your compound is on that list.
5. Outliyr Peptide Dosing Tool
Outliyr’s calculator covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class peptides. It sits inside a larger health optimization site, so the surrounding content is dense, but the calculator itself is functional and free.
*Quick honest aside: none of these tools, including the ones I rate highest, constitute medical advice. Your prescribing or supervising provider sets the dose. These tools only help you measure it.*
6. PeptideDeck
Clean, minimal interface. You enter the peptide amount in mg, the BAC water volume in mL, and your target dose in mcg. It returns the per-mL concentration alongside the exact draw volume expressed in both mL and insulin units. No extras. Does the job without friction.
7. peptidereconstitutecalculator.com
BPC-157 specific. If that is the only peptide you are working with, this one is purpose-built: mcg to units on a U-100 syringe, nothing else to configure. Narrow scope done well.
8. Prime Peptides Calculator
Part of the Prime Peptides site. Straightforward reconstitution math. Useful as a quick double-check, particularly if you are already using that vendor and want everything in one place.
9. peptides.org Dosage Charts
Not an interactive calculator, more a reference library. But the dosage charts for common peptides are detailed and the site has been around long enough to have a track record. Useful for sanity-checking a target dose before you run it through a calculator.
10. Generic Insulin Unit Converter (Spreadsheet Method)
Not a named tool, but worth including: a simple spreadsheet you build yourself. The formula is identical for every lyophilized peptide. (Dose in mcg divided by concentration in mcg per mL) times 100 equals units to draw on a U-100 syringe. If you understand that formula, you can audit any calculator above.
11. Peptide-Specific Forum Pinned Calculators
Several research-focused forums maintain pinned, community-vetted calculators updated by moderators. Quality varies, but the active ones get corrected quickly when errors surface. Worth knowing they exist, especially for less-common peptides not covered by the named tools.
12. Your Compounding Pharmacy’s In-House Guide
Underrated. A 503A compounding pharmacy will often provide a dosing and measurement guide specific to the exact vial concentration they dispensed. That is the most accurate starting point because the concentration is verified, not assumed. Use it first, then cross-check with any tool above.
A Few Things Every Calculator Should Remind You
Adding more BAC water does not change the total peptide in the vial. It changes the concentration, which changes the units you draw to hit the same dose. Most healing peptides like BPC-157 and TB-500 are dosed in micrograms, typically 250 to 500 mcg per injection. A standard U-100 syringe holds 100 units per full mL. Ten units equals 0.1 mL. Keep those numbers in your head and every calculator becomes easier to check.
Common Questions
Does it matter which calculator I use if the math is the same?
It matters more than it seems. The underlying formula is identical across tools, but what differs is how each one handles unit type, mg-vs-mcg input, and BAC water volume. A tool like FormBlends that shows its work lets you catch an input error. An anonymous tool that just returns a number gives you nothing to check against.
Why does PeptideFox suggest a specific BAC water amount instead of just accepting whatever I enter?
Because the amount of water you add directly determines where your dose falls on the syringe barrel. PeptideFox is trying to get your target dose to land on a whole, readable unit mark rather than somewhere between tick marks. That reduces measurement error at the point of drawing, which is where most mistakes actually happen.
Can I use the FormBlends calculator for tirzepatide or semaglutide, or is it only for healing peptides like BPC-157?
FormBlends includes a GLP-1 preset at 50 mg, which covers the concentration range common for compounded semaglutide. MyPeptideMatch explicitly lists tirzepatide and semaglutide. If you are working with GLP-1 class compounds, both of those are better starting points than tools built purely around research peptides.
The LeadWest calculator lists retatrutide. Is that unusual for a peptide calculator?
Yes, fairly unusual. Retatrutide is a newer triple-receptor agonist and most calculators have not added it yet. LeadWest skewing toward a clinical audience likely explains the inclusion. If your compound is retatrutide, LeadWest and MyPeptideMatch are the only named tools in this list worth checking first.
If my compounding pharmacy gives me a measurement guide, do I still need any of these tools?
The pharmacy guide is the most reliable starting point because it is built around the verified concentration of your specific vial. Use it as your primary reference. A second calculator like PeptideFox or the spreadsheet formula is worth running as a cross-check, not as a replacement, since transcription errors and label misreads do happen.
Sources
- U-100 insulin syringe standard: FDA and insulin syringe manufacturer labeling (publicly documented)
- PeptideFox feature descriptions: peptidefox.com (reviewed 2025)
- MyPeptideMatch peptide coverage: mypeptidematch.com (reviewed 2025)
- LeadWest Medical calculator: leadwestmedical.com (reviewed 2025)
- Outliyr peptide tool: outliyr.com (reviewed 2025)
- FormBlends app and calculator: App Store and Google Play listings plus web tool (reviewed 2025)
- peptides.org dosage reference: peptides.org (publicly available)
- General reconstitution math: standard pharmaceutical compounding references
