Most peptide calculators online are anonymous pages with zero accountability. A few are genuinely useful. Here is how they stack up.
Getting the math wrong by a factor of 1,000 (mg versus mcg is the classic culprit) is not an abstract risk. It is the most common serious peptide dosing error. The tools below exist to prevent exactly that kind of mistake.
1. FormBlends Peptide Calculator
Verdict: Best overall for anyone who wants to see the math, not just trust it.
The single feature that separates this one from most of the field: it shows every step of the calculation on screen so you can verify the output yourself rather than accepting a black-box answer.
You type in the vial size (mg or mcg), how much bacteriostatic water you added, and your target dose. It returns the exact units to draw on an insulin syringe, the resulting concentration per mL, and a visual syringe-fill bar showing where that dose sits on the barrel. It handles the mg-to-mcg conversion automatically because confusing those two units by a factor of 1,000 is where most mistakes happen.
It defaults to U-100 syringes but also covers U-50 and U-40, which matters if your pharmacy supplies something other than the standard U-100. One-tap presets for BPC-157 (5 mg and 10 mg vials), TB-500 (5 mg), ipamorelin (10 mg), tesamorelin (2 mg), and a GLP-1 50 mg option mean you do not have to enter the same numbers repeatedly. A companion iOS/Android app adds a 55-compound library, dose logging, and an injection-site rotation map.
No sign-up. No account. Built by a company that also operates a 503A compounding pharmacy, so there is a real organization behind it rather than a domain registered by nobody.
Rating: Top pick.
2. PeptideFox
Verdict: Strong visual UX, solid peptide breadth.
Covers more than 30 peptides and, notably, optimizes BAC water volume recommendations to produce clean unit draws on standard syringes. An illustrated step-by-step breakdown covers the reconstitution process. Good choice if you want a visual walkthrough alongside the numbers.
Rating: Highly recommended.
3. MyPeptideMatch
Verdict: Free, covers newer GLP-1 agents that many calculators miss.
Handles BPC-157, TB-500, semaglutide, and tirzepatide among other injectables. The GLP-1 coverage is useful given how many people are now working with those compounds.
Rating: Worth using.
4. LeadWest Medical
Verdict: Solid list of supported compounds, medically branded.
Covers retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. Having retatrutide on the list puts it ahead of several competitors that have not caught up with the newer GLP-1 class peptides yet.
Rating: Recommended.
5. Outliyr Peptide Calculator
Verdict: Good compound coverage, health-optimization audience.
Handles BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class compounds. The site is aimed at a biohacking audience, which means the surrounding content leans opinionated, but the calculator itself is functional.
Rating: Solid secondary option.
6. PeptideDeck
Verdict: Clean three-field interface, no extras, does the job.
Enter milligrams of peptide, mL of BAC water added, and your target dose in micrograms. It outputs concentration and the exact draw volume, including the insulin-unit equivalent. No presets, no frills. Fast to use on a phone.
Rating: Good for quick calculations.
7. peptidereconstitutecalculator.com
Verdict: BPC-157 specialists only, nothing else.
Purpose-built for one compound. Converts mcg doses to U-100 syringe units for BPC-157 specifically. If that is all you need, it works. If you ever move to a second peptide, you will need a different tool.
Rating: Narrow but functional.
8. Prime Peptides Calculator
Verdict: Straightforward reconstitution math, vendor-adjacent.
A basic calculator from a peptide vendor. Does the standard concentration and draw-volume math. The vendor connection is worth keeping in mind, though the calculator itself performs standard arithmetic the same way any other tool would.
Rating: Acceptable, use alongside an independent source.
9. peptides.org Dosage Charts
Verdict: Reference material, not a real calculator.
Static dosage charts rather than an interactive tool. Useful for cross-checking common dose ranges for research peptides, but it will not tell you how many units to draw for your specific vial and water volume. Treat it as a reference, not a calculator.
Rating: Good supplement, not a standalone dosing tool.
Before You Open Any of These Tabs
None of the tools listed here prescribe a dose, and neither does this article. They do math. Getting the correct dose in the first place is a question for a qualified medical provider who knows your situation. The reconstitution math is the same for any lyophilized peptide (more BAC water changes the units drawn per dose, not the total amount of peptide in the vial), but that mechanical fact does not substitute for clinical guidance on what dose is appropriate for you.
Common Questions
Does it matter which syringe type you enter into a peptide calculator?
Yes, it matters a lot. U-100, U-50, and U-40 syringes have different unit scales, so the same draw volume represents a different dose depending on which barrel you are using. FormBlends and PeptideFox both let you specify syringe type. If a calculator assumes U-100 and you are using U-40, your dose calculation will be wrong by a factor of 2.5.
Which of these calculators actually supports tirzepatide and semaglutide?
MyPeptideMatch is the clearest option here. It lists both semaglutide and tirzepatide alongside traditional peptides like BPC-157 and TB-500. LeadWest Medical and Outliyr cover GLP-1 class compounds more generally, but if you need confirmed tirzepatide support specifically, MyPeptideMatch is the one to check first.
Why does adding more BAC water change the units I draw but not the total peptide in the vial?
The peptide mass is fixed once the vial is sealed. Adding more bacteriostatic water dilutes the concentration, so you draw a larger volume to get the same dose in micrograms. A calculator like PeptideDeck makes this visible: change the mL field and watch the draw volume increase while the dose stays constant. The vial still contains exactly what it contained before.
Is the FormBlends calculator connected to a vendor selling peptides, and does that affect the math?
FormBlends operates a 503A compounding pharmacy, which is a regulated category under FDA oversight, not an unregulated research-chemical vendor. The calculator itself does standard arithmetic that any independent tool would replicate. The pharmacy connection means there is an identifiable organization behind the tool, which is more accountability than most anonymous calculator pages offer.
When should you use peptides.org charts alongside one of the interactive calculators?
Use the peptides.org static charts to cross-check whether a target dose falls within a documented range for a given compound before you run the reconstitution math. The charts do not replace a calculator because they cannot account for your specific vial size or water volume. Think of them as a sanity-check step, not the final calculation.
Sources
- U-100 syringe specifications: FDA device labeling standards
- BPC-157 and TB-500 typical research dose ranges: peptides.org published charts
- mg-to-mcg conversion error documentation: general pharmacology compounding references
- Tool features: direct inspection of each calculator’s public web interface, 2025-2026
