The most common mistake people make when drawing a peptide dose has nothing to do with the syringe itself. It’s a unit confusion. Someone reads “250 mcg” on a protocol sheet, types 250 into a calculator field that expects milligrams, and pulls a dose one thousand times off. That’s not a rounding error. Insulin syringe math looks simple until the mg-to-mcg conversion slips through, and that’s where most errors live.
These five tools approach the same underlying problem from different angles. No single one fits every situation, so the groupings below are by use-case rather than a straight ranking.
Best All-Around Pick for Accuracy and Transparency
FormBlends Peptide Calculator
Most web calculators give you an answer and ask you to trust it. This one shows the arithmetic on screen so you can follow each step. You put in three things: the vial size (in mg or mcg), how many mL of bacteriostatic water you added, and the dose you intend to inject. It returns the concentration per mL, how many units to draw on your syringe, and how many injections the vial will yield.
What makes it worth calling out specifically: it handles U-100, U-50, and U-40 syringes, not just the default U-100 that most tools assume. The mg-versus-mcg conversion happens automatically, with a note explaining why it matters. A visual fill bar shows exactly where on the barrel your dose should land, which is genuinely useful when you’re learning.
One-tap presets cover BPC-157 (5 mg and 10 mg vials), TB-500, ipamorelin, tesamorelin, and a GLP-1 class entry at 50 mg. Any lyophilized peptide will work too, because the reconstitution math is universal across compounds.
No signup. No account. Free. It also lives inside a mobile app (iOS and Android) that adds dose logging, an injection-site rotation map, and a library covering 55 compounds. The tool is produced by FormBlends, a company that also operates a 503A pharmacy, so there’s a named organization behind it rather than an anonymous web page.
One honest note: this tool calculates how to measure a dose you’ve already been given by a provider. It does not suggest what that dose should be.
Best for Researching a Specific Compound
PeptideFox
PeptideFox supports over 30 named peptides and does something others skip: it suggests a BAC water volume chosen to make the resulting units come out as clean numbers on a U-100 syringe. Less hunting for an awkward mark on the barrel. The site also includes a visual guide, which helps people who are newer to the process.
peptidereconstitutecalculator.com
Narrow focus, done well. This one is built specifically for BPC-157, converting mcg doses directly to U-100 insulin syringe units. If that’s the only compound you’re working with and you want a dead-simple interface, it does the job without distraction.
Best for GLP-1 and Newer Injectables
MyPeptideMatch
One of the few free tools that includes semaglutide and tirzepatide alongside the older research peptides. It also covers BPC-157 and TB-500. Useful if you’re dealing with a mix of older and newer injectable compounds on the same protocol.
Outliyr
Outliyr covers a similar compound list, including GHK-Cu, the CJC-1295/ipamorelin pairing, and GLP-1 class peptides. The site leans toward a wellness-information format, so the calculator sits alongside editorial content rather than standing alone.
Best for Broader Clinical Reference
LeadWest Medical
This one includes retatrutide, which most calculators haven’t added yet. The compound list runs through tesamorelin, sermorelin, GHK-Cu, BPC-157, TB-500, ipamorelin, and CJC-1295. Format is straightforward and clinical-leaning.
One Thing Every Calculator Gets Right (and One It Can’t Fix)
All of these tools rest on the same fact: a standard U-100 insulin syringe holds 100 units per full mL. So 10 units equals 0.1 mL. Adding more BAC water to a vial changes what you draw but not the total peptide available. Every tool above handles that correctly.
What no calculator can fix is a wrong starting dose. These tools measure. They don’t prescribe. The numbers you enter should come from a qualified provider, and any protocol involving injectable compounds deserves that level of oversight.
Common Questions
Does it matter which syringe type I enter into FormBlends if I only own U-100 syringes?
It matters a lot if you ever switch. The FormBlends calculator supports U-100, U-50, and U-40 syringes because the same unit mark means a different volume on each barrel. A U-40 syringe draws 2.5 times more liquid per unit than a U-100. Entering the wrong type produces a measurement error that compounds the further you are from a round number.
Why does PeptideFox suggest a specific BAC water volume rather than letting me enter my own?
Because awkward concentrations produce awkward draw marks. If you reconstitute a 5 mg vial with 2.5 mL, your doses often land between printed lines on the barrel. PeptideFox works backward from clean unit values on a U-100 syringe to recommend a water volume that keeps your draws on readable marks, which reduces the chance of eyeballing the wrong line.
Is peptidereconstitutecalculator.com useful for anything besides BPC-157?
Not really, and that’s intentional. The tool converts mcg doses to U-100 syringe units for BPC-157 specifically. It doesn’t handle variable vial sizes or other compounds. If your only compound is BPC-157 and you want a single-purpose, distraction-free interface, it works well for exactly that and nothing more.
MyPeptideMatch and Outliyr both cover semaglutide. How do I decide between them?
The practical difference is format. MyPeptideMatch presents the calculator as the main feature, with minimal surrounding content. Outliyr wraps its calculator inside longer wellness-oriented editorial material. If you want to read background information alongside the math, Outliyr fits that. If you want the number and nothing else, MyPeptideMatch is faster to use.
LeadWest Medical lists retatrutide when almost no other calculator does. Does that mean the math is different for it?
The underlying unit math is identical. Vial size divided by reconstitution volume gives concentration, and that concentration divided into your dose gives units to draw. Retatrutide just isn’t in most tools’ compound libraries yet. LeadWest having it listed means the preset is there, not that the formula is unique to that peptide.
*The information above describes publicly available tools and how they work mechanically. Nothing here constitutes dosing advice, medical guidance, or endorsement of self-administration. Talk to a licensed provider before handling any injectable compound.*
Sources
- U-100 syringe unit conventions: standard insulin syringe labeling (FDA-recognized format)
- FormBlends Peptide Calculator: FormBlends product documentation and app store listings
- PeptideFox: peptidefox.com public tool description
- MyPeptideMatch: public tool listing
- LeadWest Medical: public calculator page
- Outliyr: public wellness reference site
- peptidereconstitutecalculator.com: public single-compound tool
