Something shifted in the last year or so. A handful of new free calculators appeared online right around the time GLP-1 peptides like semaglutide and tirzepatide went semi-mainstream, and the older tools that had been sitting dormant since the SARMs era got quietly updated. The space is messier than it looks. Most of what you find is an anonymous webpage with no company name, no update date, and math you simply have to trust. A few tools are genuinely useful. This list covers seven I looked at seriously.
What I Was Looking For
I cared about four things: whether the math is shown (not just a black-box answer), whether it handles the mg-to-mcg conversion automatically (that 1,000x mistake is the most common dangerous error in this whole process), whether it covers the syringes most people actually own, and whether there is any real organization behind it. I also checked whether each tool explains *why* adding more bacteriostatic water changes the units you draw without changing the total dose in the vial. That one concept trips up almost everyone who is new to this.
The 7 Tools
1. FormBlends Peptide Calculator
Start here if you are learning from scratch. The single fact that sets it apart is this: the calculator shows you the arithmetic step by step, so you can follow the logic rather than just accept a number. You put in the vial size (mg or mcg), the volume of BAC water you added, and your target dose per injection. It spits out the concentration per mL, the number of units to draw, and the number of doses remaining. It handles U-100, U-50, and U-40 syringes, which matters because not everyone uses the same barrel. One-tap presets for BPC-157 (5mg and 10mg vials), TB-500, ipamorelin, tesamorelin, and a 50mg GLP-1 option cut setup time considerably. The tool lives on the web, no account needed, and the same engine is inside the FormBlends iOS/Android app, which adds a 55-compound reference library and a dose-log with injection-site rotation. It is built by a company that also runs a 503A compounding pharmacy, which at least means there is an identifiable entity behind it. Dosing guidance is not something this tool provides. That is your prescriber’s job.
2. PeptideFox
PeptideFox (peptidefox.com) is probably the most visually polished of the anonymous tools. It supports more than 30 peptides by name, and it does something I found genuinely useful: it suggests a BAC water volume that produces clean, whole-unit draws on a standard insulin syringe. If you have ever wound up trying to draw 17.3 units, you know why that matters. It also includes a visual guide to the reconstitution process. There is no company page, no team, no contact info that I could find.
3. MyPeptideMatch
Free, no account, covers BPC-157, semaglutide, tirzepatide, and TB-500 among others. The coverage of GLP-1 injectables is what makes it worth bookmarking separately. Many older peptide calculators predate semaglutide’s research-use popularity and simply do not include it. This one does. Straightforward interface, nothing fancy.
4. LeadWest Medical
The LeadWest calculator covers retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. Retatrutide specifically is hard to find in other tools. LeadWest presents as a medical organization rather than a hobbyist page, which gives it a different tone. Useful if your list includes the longer-chain healing peptides or the newer triple agonists.
5. Outliyr
Outliyr’s calculator covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and the GLP-1 class. The site itself is a broader health-optimization publication, so the calculator is one section among many. That context is either reassuring or distracting depending on what you came for. The peptide list overlaps heavily with LeadWest. Worth checking if you already read the Outliyr site for other reasons.
6. PeptideDeck
PeptideDeck takes a deliberately minimal approach. You enter three numbers: mg of peptide in the vial, mL of BAC water added, and your target dose in mcg. It returns the concentration, the volume to draw in mL, and the equivalent insulin units. No presets, no frills. Concentration shown per mL is a detail that some other tools skip, and it matters when you are trying to sanity-check your setup against a protocol you read somewhere else.
7. peptidereconstitutecalculator.com
Narrow but useful. This one is built specifically around BPC-157 and outputs in mcg-to-units on a U-100 scale. If BPC-157 is the only thing you are working with right now and you want the simplest possible interface, this does the job. Not a general-purpose tool. Do not expect it to handle anything else.
How to Choose
If you are new, use a tool that shows the math. Full stop. Black-box answers are fine once you understand what is happening, but the mg-to-mcg conversion alone has caused serious accidental overdoses and you want to see exactly where your numbers come from. FormBlends and PeptideDeck both show the arithmetic. If you are working with a less common peptide like retatrutide, LeadWest or MyPeptideMatch give you the best coverage. If BAC water volume optimization matters to your workflow, PeptideFox is worth a look. For anything GLP-1-related specifically, MyPeptideMatch and Outliyr both include that class where older tools do not.
None of these tools replace a prescribing provider. They are measurement aids. The dose itself should come from someone qualified to recommend it.
Common Questions
Does it matter which BAC water volume you enter into the calculator?
Yes, and this is where most errors happen. The total peptide in the vial does not change, but every mL of BAC water you add changes the concentration and therefore the units you draw per dose. Enter the exact volume you actually used. A 1mL difference on a 5mg vial of BPC-157 shifts your draw by roughly 20 units on a U-100 syringe.
Why does PeptideFox suggest a specific BAC water volume instead of letting you type one in freely?
It is trying to get you to a whole-number draw on a standard insulin syringe. Fractional units like 17.3 are easy to misread and hard to measure accurately. By back-calculating the water volume from a clean unit number, PeptideFox reduces that ambiguity. Whether you follow its suggestion or override it with your own volume is up to you.
Can the FormBlends calculator handle tirzepatide, or is it mainly built around the older healing peptides?
It includes a 50mg GLP-1 preset, which covers tirzepatide and semaglutide vial sizes common in compounded formats. The 55-compound library in the app version extends this further. For retatrutide specifically, LeadWest is the better option since FormBlends does not list it by name.
If two calculators give me different unit draws for the same inputs, which one should I trust?
Check whether both tools agree on concentration first. Divide the vial’s total mcg by the mL of BAC water you added. If one calculator’s stated concentration does not match that arithmetic, it has an error. The tool that shows its intermediate steps, like FormBlends or PeptideDeck, is easier to audit for exactly this reason.
Is peptidereconstitutecalculator.com useful for anything beyond BPC-157?
Not really. It was built for one compound and one syringe type. If you are also working with TB-500, ipamorelin, or any GLP-1 peptide, you will need a second tool. Using it alongside MyPeptideMatch or LeadWest covers most common research peptide combinations without much overlap.
Sources
- U-100 insulin syringe volume standard: American Diabetes Association insulin administration guidelines
- BAC water reconstitution principles: USP compounding monographs (general chapters on sterile preparations)
- Peptide dosing ranges (BPC-157, TB-500): published pre-clinical literature via PubMed
- Tool feature verification: direct inspection of each listed web tool, January 2026
