The single most common mistake I see when people start working with research peptides is treating 1 mg and 1 mcg as the same thing. They are not. They are 1,000 times apart. Someone reads a protocol calling for 500 mcg of BPC-157, confuses it with 0.5 mg, and either draws nothing useful or ten times too much. A good calculator catches that before the syringe is in hand.
Here is how I decided which tools are worth bookmarking, and how ten real options stack up.
How I Judged These Tools
Syringe-type support. Most people own U-100 insulin syringes (100 units per 1 mL). Some use U-50 or U-40. A tool that assumes U-100 only can silently give wrong answers.
Transparency. Does it show the math, or just hand you a number? Showing the math lets you catch a typo in your own inputs.
mg/mcg handling. Does it force you to pick a unit, or does it auto-convert? The conversion step is where errors happen.
Peptide coverage. Some tools are locked to one compound. Others work for any lyophilized peptide because the reconstitution formula is the same regardless of what is in the vial.
Accountability. Is there a real company behind it, or is it an anonymous page that could vanish or silently update its formulas?
The 10 Tools
1. FormBlends Peptide Calculator
My top pick. Not because it has the flashiest interface, but because it is the only free web calculator I found that shows its work and comes from an identifiable company rather than a nameless webpage.
You put in three numbers: what is in the vial, how much bacteriostatic water you added, and your target dose. It gives you the concentration, the exact insulin-unit fill, and a visual bar on a syringe graphic so you can see where the plunger stops. It also handles the unit conversion automatically, which is the part that trips people up. The math is printed out in plain numbers so you can check it yourself.
It supports U-100, U-50, and U-40 syringes, which matters if you are not using the most common syringe size. One-tap presets cover BPC-157 (both 5 mg and 10 mg vials), TB-500, ipamorelin, tesamorelin, and GLP-1 class peptides, but you can enter any lyophilized peptide because the underlying math is identical across compounds.
No account needed. No signup. The same calculator lives inside the FormBlends mobile app alongside a 55-compound reference library, dose logging, and an injection-site rotation tracker. The company that built it also operates a 503A compounding pharmacy, so there is a real business name attached to what you are using.
One important note: it does not tell you what dose to take. It only converts a dose you have already been given into syringe units. That is the right boundary for a measurement tool.
2. PeptideFox
Found at peptidefox.com. Covers more than 30 named peptides and includes a visual guide to reading the syringe. Its standout feature is optimizing the BAC water volume to produce clean, whole-unit draws, which reduces rounding error. Good choice if you want compound-specific guidance rather than a blank-entry calculator.
3. MyPeptideMatch
Free, no login, covers BPC-157, TB-500, semaglutide, tirzepatide, and several other injectables including GLP-1 class compounds. Useful for people managing weight-loss peptides alongside healing peptides in the same protocol.
4. LeadWest Medical
A clinical-leaning calculator that includes retatrutide alongside the more common healing peptides: BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. The retatrutide inclusion is rare among free tools.
5. Outliyr
Covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class peptides. Outliyr is primarily a health-optimization information site; the calculator is one feature among many, which means the surrounding context is more editorial than the standalone tools.
6. PeptideDeck
Straightforward input: vial size in mg, BAC water in mL, target dose in mcg. Outputs concentration and the exact draw volume in both mL and insulin units. Clean and fast. No frills, no presets. Works well for anyone comfortable entering their own numbers.
7. peptidereconstitutecalculator.com
Narrow focus. Built specifically for BPC-157, converting mcg doses to units on a U-100 syringe. If BPC-157 is the only compound in your protocol, this is quick and purpose-built. Not useful beyond that one peptide.
8. Prime Peptides Calculator
Bundled with the Prime Peptides vendor site. Functional reconstitution math. Like most vendor-attached calculators, it is most convenient if you are already buying from that source, but the math is the same math regardless of who hosts it.
9. peptides.org Dosage Charts
Not a live calculator. Static reference charts for common peptides. Useful for double-checking typical dose ranges before you enter numbers into a calculator, not a substitute for one.
10. Manual Spreadsheet
Old-fashioned. The formula is: (target dose in mcg divided by total mcg in vial) multiplied by total BAC water in mL, then multiplied by 100 to get U-100 units. Takes two minutes to build in any spreadsheet app. Zero dependency on a website staying online. Worth knowing even if you use one of the tools above.
Quick Comparison
| Tool | Syringe Types | Shows Math | Any Peptide | Free |
| FormBlends | U-100, U-50, U-40 | Yes | Yes | Yes |
| PeptideFox | U-100 | Partial | 30+ named | Yes |
| MyPeptideMatch | U-100 | No | Several | Yes |
| LeadWest Medical | U-100 | No | Several | Yes |
| Outliyr | U-100 | No | Several | Yes |
| PeptideDeck | U-100 | Partial | Yes | Yes |
| peptidereconstitutecalculator.com | U-100 | No | BPC-157 only | Yes |
| Prime Peptides | U-100 | No | Several | Yes |
| peptides.org charts | N/A | N/A | Reference only | Yes |
| Manual Spreadsheet | Any | Yes | Yes | Free |
Bottom Line
Start with a tool that shows you the math and supports whatever syringe you own. Get your dose from a qualified provider first. The calculator’s only job is to translate that dose into a line on a syringe barrel. Done right, it is a boring, reliable step. Done wrong, it is the most expensive math mistake you will make.
Common Questions
Does it matter which peptide calculator you use if the reconstitution math is the same?
It matters more than people expect. The underlying formula is identical across compounds, but tools differ in whether they show intermediate steps, support your syringe type, and handle mg-to-mcg conversion without asking you to do it manually. A tool that silently assumes U-100 when you own a U-40 syringe will give you a wrong draw every time.
Can the FormBlends calculator handle a 10 mg BPC-157 vial, or is it built around the more common 5 mg size?
Both. FormBlends includes one-tap presets for 5 mg and 10 mg BPC-157 vials specifically. You can also ignore the presets entirely and type in any vial size, so it works if your compounding pharmacy sends a non-standard amount.
Why does PeptideFox optimize the BAC water volume instead of just accepting whatever you enter?
Rounding error. If your target dose does not divide evenly into whole syringe units at a given concentration, the draw falls between tick marks and you have to estimate. PeptideFox suggests a BAC water volume that lands your dose on a clean unit mark, which removes that guesswork. It is a small thing that makes a real difference at low doses.
Is the peptidereconstitutecalculator.com tool actually safe to use for compounds other than BPC-157?
It was not built for that. The site is purpose-built for BPC-157 on a U-100 syringe. Entering a different peptide would produce a number, but there is no compound-specific validation, and the tool gives no indication it was tested beyond its intended use case. Use a general-entry calculator like PeptideDeck or FormBlends for anything else.
If I already have the manual spreadsheet formula, what does a tool like FormBlends actually add?
Speed and error-checking. The formula itself takes seconds to run, but entering three numbers into a spreadsheet still requires you to keep track of units, remember to convert mg to mcg before dividing, and interpret the decimal output as a syringe position. FormBlends handles the conversion, displays the result as both mL and insulin units, and overlays it on a syringe graphic so the visual matches what you are holding.
Sources
- peptidefox.com, public tool documentation
- mypeptidematch.com, public tool interface
- leadwestmedical.com, calculator page
- outliyr.com, peptide calculator feature
- peptidedeck.com, public tool
- peptidereconstitutecalculator.com, public tool
- peptides.org, dosage reference charts
- FormBlends web calculator and app store listings (iOS/Android)
- General pharmacology reference: U-100 insulin syringe standardization, FDA guidance on insulin concentration labeling
