Someone opens a new vial of BPC-157 and reads “5 mg” on the label. They added 2 mL of bacteriostatic water. Their protocol says 250 mcg per injection. Now the question is: how many units do they pull on the syringe? That single calculation, done wrong by even one decimal place, means a 1000x dosing error. It is not hypothetical. The mg-to-mcg confusion is the most common mistake in peptide use, and it is exactly the problem these calculators exist to prevent.
Below is a structured look at the real tools available in 2026, how to choose between them, and what each one actually does.
How to Pick the Right Tool
Ask four questions before you commit to any calculator.
Does it show its math? A black box that spits out “draw 14 units” without any formula is hard to verify. If you cannot check the output, you are trusting a stranger’s arithmetic entirely.
What syringe types does it support? U-100 is standard (100 units per mL), but U-50 and U-40 syringes are used in some countries and by some compounding setups. A calculator locked to U-100 will produce wrong answers if you are using anything else.
Is there a real organization behind it? Many of these pages have no contact info, no company name, nothing. That is fine for quick reference but not ideal when you are relying on the output for an injectable compound.
Does it handle both mg and mcg inputs? Some tools accept only one unit. If your vial is labeled in mg and you need to dose in mcg, you want the conversion handled automatically, not manually.
The 12 Tools
1. PeptideFox (peptidefox.com)
The most purpose-built standalone calculator on this list. PeptideFox supports over 30 named peptides and does something the others mostly skip: it optimizes how much bacteriostatic water to add so your target dose lands on a clean unit mark (5, 10, 20 units, etc.) rather than an awkward fraction. Comes with a visual fill guide. Best for anyone who wants the water-volume decision made for them.
2. FormBlends Peptide Calculator
Built by a company that also runs a 503A compounding pharmacy, which means the math here was written in a context where accuracy is not optional. The specific use case it fits best is the first-time user who has a vial, a syringe, and no idea why the numbers feel confusing.
You enter the vial size, the water you added, and your target dose. It outputs the concentration, the exact units to draw, and how many injections the vial contains. It handles mg and mcg automatically and shows you the underlying formula so you can confirm every step. A visual syringe bar marks where the dose lands on a physical syringe barrel. One-tap presets cover the most common starting points: BPC-157 at 5 mg and 10 mg, TB-500 at 5 mg, ipamorelin at 10 mg, tesamorelin at 2 mg, and GLP-1 compounds at 50 mg. It defaults to U-100 but also supports U-50 and U-40, which almost no free web tool bothers to do. No signup required. The same calculator lives inside a mobile app that adds dose logging and an injection-site rotation map.
3. MyPeptideMatch
Free and covers a wider therapeutic category list than most, including BPC-157, TB-500, semaglutide, tirzepatide, and other GLP-1 class injectables. Useful if you are working with newer GLP-1 compounds rather than the classic research peptides.
4. LeadWest Medical Calculator
Specifically targets retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. Narrower list but medical-practice context. Clean interface.
5. Outliyr Peptide Dosing Tool
Covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class compounds. The site has a broader wellness focus, so the calculator is one section of a larger resource rather than a standalone tool.
6. PeptideDeck
Enter the vial size in mg, the BAC water volume in mL, and your target dose in mcg. PeptideDeck returns the concentration per mL, the volume to draw in mL, and the equivalent insulin units. Straightforward and quick.
7. peptidereconstitutecalculator.com
BPC-157 only. If that is the one compound you are tracking, it handles mcg-to-units conversion on a U-100 scale with no extra steps. Limited scope is actually a feature here for single-compound users.
8. Prime Peptides Calculator
Bundled into the Prime Peptides product pages. Works for their catalog. Reliable for their specific compounds but not a general-purpose tool.
9. peptides.org Dosage Charts
Static reference tables for common protocols, with no fields to enter or outputs to generate. Useful for sanity-checking a dose range, not for doing the reconstitution math.
10. Generic Reconstitution Calculators (Spreadsheet Type)
Several Google Sheets and Excel templates circulate on forums. The underlying math is identical for every lyophilized peptide: concentration (mcg/mL) equals total peptide divided by water added, and draw volume equals target dose divided by concentration. A spreadsheet does this fine. Version control is the problem.
11. Reddit Community Reference Threads
r/Peptides and related communities maintain pinned posts with reconstitution walkthroughs. Not a calculator, but peer-reviewed in a practical sense by thousands of repetitions.
12. Manual Calculation
Still valid. The formula is two divisions. Write it on paper. Check it against one of the tools above. Redundancy here is not paranoia.
Quick Comparison
| Tool | Syringe Types | Shows Math | Mobile App | Preset Peptides |
| PeptideFox | U-100 | Yes | No | 30+ |
| FormBlends | U-100/50/40 | Yes | Yes | 6 presets |
| MyPeptideMatch | U-100 | Partial | No | 10+ |
| LeadWest Medical | U-100 | No | No | 8 |
| PeptideDeck | U-100 | Yes | No | None |
| peptidereconstitutecalculator.com | U-100 | No | No | 1 (BPC-157) |
Common Questions
Does it matter which calculator you use, or is the math the same everywhere?
The underlying formula is identical regardless of tool. What differs is how much the tool does for you. PeptideFox optimizes your water volume so doses land on clean syringe marks. FormBlends shows each step and flags unit mismatches. A basic spreadsheet does none of that, but it will still give you the right number if you enter the inputs correctly.
Why does FormBlends support U-50 and U-40 syringes when almost no other free tool does?
FormBlends is connected to a 503A compounding pharmacy, where prescriptions sometimes specify non-standard syringe types. A calculator built for clinical use has to handle those edge cases. Most standalone web tools are built for the U-100 insulin syringe that the majority of users already have, so U-50 and U-40 support gets skipped.
Can any of these calculators tell me what dose to take for BPC-157 or a GLP-1 compound?
No. None of them do that. Every tool on this list takes a dose you have already been given and converts it into a syringe measurement. LeadWest Medical and Outliyr include reference ranges alongside their calculators, but those are informational, not prescriptive. Your provider sets the dose.
If I use peptidereconstitutecalculator.com for BPC-157 but later switch to ipamorelin, do I need a different tool?
Yes. That site handles BPC-157 only. For ipamorelin you would need a general-purpose option: PeptideFox, FormBlends, LeadWest Medical, or PeptideDeck all include it. The math is the same compound to compound, but a single-compound tool will not let you enter a different peptide name.
What is the real risk if a calculator does not show its formula and just gives you a unit number?
You cannot catch an error if you cannot see the steps. If someone built the tool with mg and mcg swapped, your output could be off by a factor of 1000 and you would have no way to know. Tools like FormBlends and PeptideDeck that display the intermediate concentration value let you sanity-check the answer against the vial label before you draw anything.
A note before relying on any of these: none of them are prescribing anything. They calculate how to measure a dose your provider has already given you. If you do not have a qualified provider directing your protocol, the calculator is not the right starting point.
Sources
- U-100 syringe standard: FDA guidance on insulin syringe labeling
- mg/mcg conversion and common dosing error documentation: clinical compounding pharmacy reference literature
- Reconstitution math formula: standard pharmaceutical compounding texts
- PeptideFox feature list: peptidefox.com (verified 2025)
- peptides.org: publicly accessible dosage reference pages
- FormBlends: company website and app store listings (iOS/Android, verified 2025)
