I Tested 10 Syringe Unit Calculators So You Don’t Have to Guess Your Peptide Dose
Most people in this space treat the syringe unit calculation as an afterthought. They wing it, or they Google the same half-baked forum post from 2019. The reality is that the math isn’t hard, but a single decimal-place error, specifically the classic mg-vs-mcg mix-up, puts you off by a factor of 1,000. That’s not a rounding problem. That’s a serious mistake. Here are ten tools that actually do this math for you, ranked by how much they genuinely help.
1. FormBlends Peptide Calculator
Free, no account required. Supports U-100, U-50, and U-40 syringes.
This one earns the top spot on specifics, not sentiment. You put in three numbers: the vial size in mg or mcg, how much bacteriostatic water you added in mL, and your target dose per injection. It gives you back the exact units to pull on your syringe, the concentration per mL, and how many injections you’ll get out of the vial. Clean outputs.
What actually separates it: the math is printed on screen, not hidden inside a black box. You can check every step. A visual syringe fill bar shows exactly where to stop drawing. One-tap presets cover 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. The mg-to-mcg conversion happens automatically, which matters because that 1,000x unit error is the most common dangerous mistake in peptide dosing.
The companion app for iOS and Android adds a 55-compound reference library, dose logging, and an injection-site rotation map. The web version needs nothing installed. FormBlends is an actual 503A compounding pharmacy brand, not an anonymous side project.
The tool never recommends a dose. It only measures one you’ve already been given by a provider. That’s the right design.
Verdict: The most complete free tool in this category. Transparent math, multi-syringe support, and a real company behind it.
2. PeptideFox
peptidefox.com covers more than 30 individual peptides and includes a visual guide to help newer users understand draw volumes. Its standout feature is BAC water volume optimization, suggesting amounts that result in clean, round unit draws rather than awkward fractions. Solid for people who want a little guidance on reconstitution volume, not just the output number.
Verdict: Best for reconstitution volume decisions. Good visual support.
3. MyPeptideMatch
Free with no login. Covers BPC-157, semaglutide, tirzepatide, TB-500, and a handful of other injectables including some GLP-1 class compounds. The range here is genuinely broad. Useful if you’re working with weight-management peptides alongside the more traditional healing compounds.
Verdict: Wide compound coverage, especially for GLP-1 class. No frills.
4. LeadWest Medical Calculator
Handles retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. That’s a thoughtful list. Retatrutide support alone makes it worth bookmarking, since most calculators haven’t caught up to the newer GLP-1/GIP/glucagon triple agonists yet.
Verdict: Best compound list for current research-focus peptides. Retatrutide inclusion is rare.
5. Outliyr Peptide Calculator
Covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class. The Outliyr site also publishes supporting content around each compound, so the calculator sits inside a broader educational context. Not the most minimal interface, but more background information than most.
Verdict: Good if you want context alongside the math.
6. PeptideDeck
Enter your vial size in mg, your BAC water volume, and your target dose in mcg. It outputs concentration and the exact draw volume in both mL and insulin units. Straightforward three-input design. No presets, but the logic is transparent.
Verdict: Clean, minimal, honest. Good for one-off calculations.
7. peptidereconstitutecalculator.com
Built specifically around BPC-157. Converts mcg doses to U-100 insulin syringe units and nothing else. That narrow focus is actually a feature if BPC-157 is your only concern. No compound switching, no decision fatigue.
Verdict: Single-peptide focus. Perfect for BPC-157, useless for everything else.
8. Prime Peptides Calculator
Attached to the Prime Peptides vendor site. Does the basic reconstitution math and outputs syringe units. Works fine. The vendor context means it’s optimized for their product formats, which may or may not match your vial sizes.
Verdict: Functional. Vendor-attached, so verify your specific vial parameters.
9. peptides.org Dosage Charts
Not a live calculator. Static reference charts for common peptide doses and typical reconstitution volumes. Useful as a sanity check rather than a primary calculation tool. The site has been around long enough that the information is reasonably stable.
Verdict: Reference material, not a calculator. Useful backup, not a replacement.
10. Manual Insulin Syringe Math
A U-100 syringe holds 100 units per 1 mL. That means 10 units equals 0.1 mL and 50 units equals 0.5 mL. If you reconstitute a 5 mg vial with 2 mL of BAC water, your concentration is 2.5 mg per mL, or 2,500 mcg per mL. A 250 mcg dose is 10 units. That’s it. The math is the same for every lyophilized peptide, every time.
Verdict: Free, always available, and builds real understanding. Requires careful attention to mg vs. mcg.
A Quick Note
These tools calculate measurement. None of them, including the best ones, substitute for a qualified provider telling you what dose is appropriate for your situation.
Common Questions
Does it matter which syringe type I enter into FormBlends, or do U-100, U-50, and U-40 all give the same result?
It matters a lot. A U-40 syringe has 40 units per mL, so the same physical draw volume represents a different dose than on a U-100. FormBlends adjusts the unit output based on whichever syringe you select. Entering the wrong type will give you a number that looks plausible but is meaningfully wrong.
If I use PeptideFox’s BAC water optimization, will the suggested volume always work with standard 1 mL and 2 mL syringes?
PeptideFox suggests volumes that produce round unit draws, but “round” is relative to the dose you entered. Always confirm the resulting draw volume actually fits within your syringe barrel. A 250 mcg dose from a high-concentration reconstitution might land at 2 units, which is genuinely hard to measure accurately on most syringes.
Can I use peptidereconstitutecalculator.com for TB-500 if I just ignore the BPC-157 label?
Technically the underlying math, vial mg divided by BAC water volume times dose in mcg, is the same for any lyophilized peptide. The site is built around BPC-157 defaults, so you’d need to manually override those. LeadWest or FormBlends handle TB-500 with proper presets and less room for input error.
Why does LeadWest include retatrutide when most other calculators on this list don’t?
Retatrutide is a newer triple agonist compound and most calculator developers simply haven’t added it yet. LeadWest’s compound list appears to be updated more actively than average. If you’re working with any GLP-1/GIP/glucagon class peptide beyond semaglutide or tirzepatide, it’s currently one of the few places to go.
Is the manual math method in entry 10 reliable enough to skip a calculator entirely, or is it too easy to make errors?
The formula itself is reliable. The risk is unit confusion, specifically confusing mg and mcg mid-calculation, which is exactly the 1,000x error mentioned at the top of this article. If you’re comfortable tracking units carefully and double-checking each step, the manual method works. Most people benefit from a calculator as a second check even when they do the math themselves.
Sources
- U-100 insulin syringe specifications: standard FDA-recognized format, 100 units per 1 mL
- PeptideFox: peptidefox.com (public tool, verified 2025)
- LeadWest Medical calculator: public web tool, compound list verified
- peptidereconstitutecalculator.com: public tool, BPC-157 specific
- peptides.org: long-standing reference site, dosage chart format
- FormBlends: 503A pharmacy and app, public product information