The most common mistake people make when reconstituting peptides has nothing to do with sterile technique. It’s a unit conversion error. Someone sees their peptide listed in milligrams, their dose listed in micrograms, forgets that 1 mg equals 1,000 mcg, and draws ten times too much. Or ten times too little. Both outcomes are bad. A decent calculator catches that before the needle goes anywhere near anyone.
Here are seven tools that actually help with the math.
1. FormBlends Peptide Calculator
This one earns the top spot for a specific reason: it shows you the arithmetic. Most calculators just spit out a number. This one displays every step, so you can confirm the logic yourself rather than trust a black box.
You enter three things: the total amount in your vial, how much bacteriostatic water you added, and the dose you intend to inject. The tool returns the concentration per mL, the exact units to draw, and how many doses the vial contains. It also displays a visual fill bar showing where that dose sits on a syringe. Small thing, genuinely useful for people still getting comfortable with insulin syringes.
The mg-to-mcg conversion is handled automatically, which is the whole point. That 1,000x error is the one the tool was built to prevent.
It supports U-100, U-50, and U-40 syringes. One-tap presets exist for BPC-157 (5 mg and 10 mg vials), TB-500, ipamorelin, tesamorelin, and GLP-1 compounds. Free, no account required. The same calculator lives inside the FormBlends mobile app alongside a 55-compound library, injection-site rotation tracking, and dose logging. FormBlends is an actual telehealth and 503A pharmacy company, not an anonymous webpage. That matters for accountability.
2. PeptideDeck
Straightforward and well-structured. You enter the vial size in mg, the volume of BAC water added in mL, and the dose you want in mcg. PeptideDeck returns the concentration, the draw volume in mL, and the equivalent insulin units. Nothing fancy, but the output fields are clearly labeled and the logic is sound. Good for single-compound quick math.
3. PeptideFox
Covers more than 30 peptides by name, which makes it one of the more peptide-specific tools on this list. The standout feature is volume optimization: it suggests a BAC water amount that results in clean, round unit draws on a U-100 syringe. Fewer awkward decimals, fewer measurement errors. There’s also a visual guide explaining the reconstitution steps. Good choice if you want something that thinks about the syringe math before you do.
4. MyPeptideMatch
Free, no login. The coverage here skews toward compounds that have entered mainstream clinical conversation, including BPC-157, TB-500, semaglutide, and tirzepatide. That last pair puts it slightly ahead of the purely research-peptide tools for anyone working with GLP-1 class compounds. The interface is clean. No visual syringe guide, but the output is accurate and the inputs are sensibly labeled.
5. LeadWest Medical
A medically branded calculator covering retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. The presence of retatrutide is notable given how recently that compound entered wider use. The medical framing also means the surrounding copy is more clinical in tone, which some users prefer. Straightforward input fields, no frills.
6. Outliyr
Covers a similar peptide list to LeadWest, including BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class. The Outliyr site is built around a broader biohacking and optimization content framework, so the calculator exists alongside a lot of editorial context. That means more reading if you want just the math, but also more explanation of what these compounds are for people newer to the category.
7. peptidereconstitutecalculator.com
Single-purpose and narrow in scope. It focuses almost entirely on BPC-157, converting mcg doses to units on a U-100 syringe. Scope is limited by design. If BPC-157 is the only peptide you are working with right now, it is a perfectly adequate quick reference. If you need anything else, look elsewhere.
A Note on All of These
The reconstitution math is the same for every lyophilized peptide. Total peptide divided by total water volume gives concentration. Dividing your intended dose by that concentration tells you exactly how many mL to draw. Multiply by 100 to get U-100 units. Any calculator doing that math correctly gives the same answer. The differences between tools come down to interface, syringe type support, peptide presets, and whether the math is shown or hidden.
None of these tools prescribe a dose. They measure one you already have. Source your target dose from a qualified provider, not a calculator.
Common Questions
If the FormBlends calculator shows every step, what exactly does that look like on screen?
It displays the concentration calculation first (total mg divided by total mL of BAC water), then the draw volume calculation (your dose in mcg divided by concentration in mcg/mL), then the unit equivalent. Each line is labeled. You can read down the chain and spot immediately if you entered something wrong, rather than wondering why the final number looks off.
Does it matter which syringe type you select in a calculator, or is that just a display preference?
It matters for the unit readout. A U-100 syringe has 100 units per mL, a U-50 has 50, and a U-40 has 40. The mL draw volume is identical regardless, but the graduation marks on the barrel are different. If you select U-100 in the calculator but you are holding a U-40 syringe, the unit number the tool gives you will send you to the wrong line on the barrel.
PeptideFox suggests a BAC water volume rather than asking you to enter one. How does that actually reduce errors?
When you choose your own water volume, you often end up with a concentration that produces awkward decimals at your target dose, say 0.073 mL on a syringe marked in 0.01 increments. PeptideFox works backward from your dose and syringe type to suggest a water volume that produces a clean, round number of units. Fewer mental rounding decisions at the syringe means fewer small measurement errors.
Can any of these calculators tell me the right dose for a compound like BPC-157 or semaglutide?
No. None of them do that, and none should. They take a dose you have already been given and convert it into a draw volume. The dose itself has to come from a prescriber or qualified clinical source. Using a calculator output to infer a starting dose is the wrong direction entirely.
Why does MyPeptideMatch include semaglutide and tirzepatide when most peptide calculators skip them?
Those two compounds are GLP-1 receptor agonists that are now widely prescribed and compounded, so the reconstitution question comes up constantly for patients using compounded versions from 503A or 503B pharmacies. Most older peptide calculators were built around research compounds and simply predate the GLP-1 wave. MyPeptideMatch reflects where clinical volume actually is right now.
Sources
- U-100 insulin syringe specifications: standard pharmacology reference (100 units per 1 mL)
- PeptideFox: peptidefox.com, publicly available tool
- MyPeptideMatch: public web tool, verified compound coverage
- LeadWest Medical: public calculator, compound list verified via site
- Outliyr: public web tool, compound list verified via site
- PeptideDeck: public web tool, input/output fields verified
- peptidereconstitutecalculator.com: public web tool, BPC-157 scope verified
- FormBlends: 503A pharmacy and telehealth company, calculator and app publicly available
