9 Online Peptide Calculators That Actually Solve the Right Problem

Most people searching for a peptide calculator already understand the reconstitution math in theory. The problem is the unit conversion, specifically the mg-to-mcg switch that trips up even experienced users. One milligram equals one thousand micrograms. Flip that by accident and you are drawing ten times the intended dose. These nine tools exist because that mistake keeps happening, and a good calculator removes it entirely.

The Rankings

1. FormBlends Peptide Calculator

The math is shown. That one design decision separates this tool from most of the field. You enter your vial size (in mg or mcg), how much bacteriostatic water you added, and the dose your provider prescribed per injection. The calculator outputs the exact units to draw on a U-100, U-50, or U-40 syringe, the concentration per mL, and the total number of doses remaining in the vial. A visual syringe fill bar marks where your plunger stops.

What makes it worth ranking first: it is built by FormBlends, an actual 503A compounding pharmacy company, not an anonymous hobby page. Because reconstitution math is universal across all lyophilized peptides, the tool works whether you enter BPC-157, tesamorelin, or anything else. One-tap presets cover common vial sizes like BPC-157 at 5 mg and 10 mg, TB-500 at 5 mg, and GLP-1 class compounds at 50 mg. No sign-up, no account, free on the web and inside the FormBlends iOS/Android app. The app layer adds a 55-compound reference library, dose logging, and an injection-site rotation map.

It does not recommend a dose. You supply the dose. It only tells you the correct volume to draw for that dose.

2. PeptideFox

peptidefox.com covers more than 30 named peptides and does something few others bother with: it optimizes the BAC water volume to produce clean, round unit draws on a U-100 syringe. A visual guide walks through where the plunger should sit. Useful for people who want a tidy 10 or 20 unit pull rather than an awkward 13.

3. PeptideDeck

Simple three-field entry. Vial mg, BAC water mL, and target dose in mcg. PeptideDeck outputs the concentration and the draw volume in both mL and insulin units. No extras. No clutter. Fast to use on a phone between refrigerator and injection.

4. MyPeptideMatch

Free, no account, covers BPC-157, semaglutide, tirzepatide, and TB-500 among other injectables. The GLP-1 coverage is a practical advantage because semaglutide vials vary widely in concentration depending on source. Dosing math for a 5 mg semaglutide vial reconstituted with 2 mL differs a lot from one reconstituted with 1 mL. MyPeptideMatch handles that input directly.

5. LeadWest Medical Calculator

LeadWest Medical’s tool is clinically oriented. The compound list includes retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. The peptide list reflects what a functional medicine or anti-aging clinic might carry. Useful if you are working through a provider rather than self-sourcing.

6. Outliyr Peptide Calculator

The Outliyr tool’s reference list spans BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and the GLP-1 class. The site is a health-optimization editorial brand, so the calculator sits inside a broader article with context. That framing makes it more approachable for someone new to reconstitution but slightly slower to reach for a repeat user.

7. peptidereconstitutecalculator.com

Narrow scope, one job done well. This site focuses almost entirely on BPC-157, walking through the mcg-to-U-100-units conversion in clear steps. It assumes a U-100 syringe (100 units per mL, 10 units per 0.1 mL). Not flexible for other peptides, but if BPC-157 is all you need, the specificity is a feature.

8. Prime Peptides Calculator

A vendor-hosted tool. Prime Peptides is a research peptide supplier, and its calculator is functional for reconstitution math. Worth knowing the calculator exists in this space, though vendor-hosted tools carry the inherent conflict of being adjacent to a sales page.

9. peptides.org Dosage Charts

Not an interactive calculator. peptides.org publishes static dosage reference charts for a range of compounds. No input fields, no unit conversion, just published reference ranges. Useful as a sanity check against your provider’s guidance, not as a primary dosing tool.

Quick Comparison Table

Tool	Interactive	Syringe Types	Peptides Covered	Account Required
FormBlends Peptide Calculator	Yes	U-100, U-50, U-40	Universal	No
PeptideFox	Yes	U-100	30+ named	No
PeptideDeck	Yes	U-100	Universal	No
MyPeptideMatch	Yes	U-100	BPC-157, GLP-1s, TB-500	No
LeadWest Medical	Yes	U-100	8+ named	No
Outliyr	Yes	U-100	7+ named	No
peptidereconstitutecalculator.com	Yes	U-100	BPC-157 focus	No
Prime Peptides	Yes	U-100	Vendor selection	No
peptides.org	No (charts)	N/A	Multiple	No

FAQ

Does adding more bacteriostatic water change the dose I get?

No. It changes the concentration per mL and therefore the volume you draw, but the total peptide in the vial stays the same. Add 2 mL instead of 1 mL and you draw twice the volume for the same dose. Every calculator on this list reflects that relationship.

What does U-100 mean and why does it matter?

U-100 means 100 units per 1 mL. A standard insulin syringe marked to 100 units holds exactly 1 mL at the top. So 10 units on that syringe equals 0.1 mL, and 50 units equals 0.5 mL. If you use a U-50 syringe instead, the same markings represent different volumes. Using the wrong syringe type without adjusting is how measurement errors happen.

Why is the mg-to-mcg conversion so dangerous to get wrong?

One mg is 1,000 mcg. If a tool or a user treats 1 mg as equal to 1 mcg, the drawn dose is off by a factor of 1,000. For a peptide dosed at 250 mcg, that error would mean drawing 250 mg, which is not physically possible from most vials but illustrates why unit clarity matters before the needle goes anywhere.

Can I use these calculators for any lyophilized peptide?

The reconstitution math, vial mg divided by water mL to get concentration, is identical regardless of the peptide. A calculator that accepts any mg and mL input works universally. Tools that only accept named peptides from a dropdown are artificially limited.

Should I trust a calculator from a peptide vendor?

The math itself is verifiable. Add the inputs yourself and check the output against basic arithmetic. The concern with vendor-hosted tools is not that they miscalculate but that the surrounding content exists to sell product. Treat the calculator independently from the storefront.

Sources

• U-100 insulin syringe standardization: FDA guidance on insulin syringe labeling
• BPC-157 and TB-500 typical research dosing ranges: published pharmacology literature via PubMed
• peptides.org dosage reference charts: peptides.org (public)
• PeptideFox feature descriptions: peptidefox.com (public)
• FormBlends calculator features and 503A pharmacy designation: FormBlends public web presence