The most common mistake people make with peptide reconstitution is not the math itself. It is the unit conversion. One milligram equals one thousand micrograms, and mixing those two up produces a dose that is either 1000x too low or, far more dangerously, 1000x too high. A calculator that forces you to enter both the vial weight and your target dose in the same step catches that error before it happens. The five tools below all do some version of that job, with different levels of depth and polish.
1. PeptideFox
This is the one you see recommended most often in forums where people actually know what they are talking about. PeptideFox supports over 30 peptides and does something the others rarely bother with: it optimizes the BAC water volume you should add based on the peptide and your target dose, so your draws land on clean unit marks instead of awkward fractions. There is also a visual guide built in. For someone who is new to reconstitution and does not yet have a feel for syringe math, that visual layer matters. It is free, no account needed, and the interface is direct.
2. FormBlends Peptide Calculator
A free web tool that also lives inside a mobile app (iOS and Android). You put in the vial’s peptide amount, the volume of bacteriostatic water you added, and your per-injection target, and it outputs the exact units to draw on an insulin syringe, the concentration per mL, and how many doses you have left. The single thing that sets it apart from most tools in this category is that it shows the actual arithmetic behind the answer, not just the result. You can check the formula yourself, which matters if you are ever working with an unusual vial size or a dose that does not match a preset.
It also handles U-100, U-50, and U-40 syringes, which is worth noting because not every country stocks U-100 as the default. The mg-to-mcg conversion is handled automatically, quietly, which is exactly where dosing errors happen most. Worth mentioning honestly: this calculator does not tell you what dose to take. You enter the dose your provider gave you, and it tells you how to measure it. That is the right scope for a tool like this.
3. PeptideDeck
Stripped down to three inputs: milligrams in the vial, milliliters of BAC water added, and target dose in micrograms. Output is concentration, draw volume in mL, and the equivalent insulin units. Simple. No presets, no extra steps. If you already know your dose and just want the syringe number fast, PeptideDeck does it without friction. Good for people who have already done the reconstitution math before and just want a quick check.
4. LeadWest Medical Calculator
LeadWest specifically names the peptides it covers, including retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. That explicit list is useful for confirming the tool accounts for the dosing ranges that actually appear in clinical practice. Retatrutide in particular is newer to the peptide space and not every calculator has caught up with it. LeadWest is attached to a medical provider context rather than being an anonymous page, which adds a small layer of accountability to the output.
5. MyPeptideMatch
Free and covers a wide range, including BPC-157, TB-500, semaglutide, tirzepatide, and other injectables. The GLP-1 class inclusion is increasingly relevant as more people outside clinical settings are working through reconstitution math for semaglutide pens and vials. Most peptide calculators were built when GLP-1 compounds were primarily research peptides, so a tool that treats them alongside BPC-157 and TB-500 without separating them into a different workflow is genuinely convenient.
Before You Run Any Numbers
A word of honest caution: most reconstitution calculators on the web are static pages with no named author, no stated accuracy review, and no update log. Use the math they produce as a starting point, then verify the arithmetic yourself with a basic formula (concentration = total mcg divided by total mL, draw volume = target mcg divided by concentration). The underlying reconstitution math is universal for any lyophilized peptide, and checking it takes thirty seconds.
None of these tools replace a qualified prescribing provider. Every dose you enter should come from a licensed clinician who knows your case.
Common Questions
Does it matter which of these calculators you use if the math is the same?
It does, for one specific reason: error prevention. Tools like FormBlends show the underlying arithmetic so you can spot a wrong input before you draw. PeptideFox goes further by suggesting how much BAC water to add in the first place. A calculator that only outputs a number gives you no way to catch a unit entry mistake before it becomes a dosing error.
Can PeptideFox and LeadWest handle vial sizes that are not standard, like a 10 mg vial instead of the usual 5 mg?
PeptideFox lets you enter a custom vial weight rather than selecting from a preset list, so non-standard sizes work. LeadWest is designed around clinical dosing ranges for the peptides it names, but the core inputs are vial amount and BAC water volume, which accommodate any vial size as long as you enter the correct number.
Why does FormBlends list U-40 and U-50 syringes when most people in the US only use U-100?
Outside the United States, U-40 insulin syringes are still the dominant format in many countries. Using a U-100 calculator with a U-40 syringe produces a 2.5x dosing error without any warning. FormBlends accounting for all three syringe types is a practical acknowledgment that not every user is drawing from the same starting point.
Is MyPeptideMatch the only one here that covers semaglutide and tirzepatide reconstitution math?
Based on the information reviewed, MyPeptideMatch is the only tool in this list that explicitly includes semaglutide and tirzepatide alongside the traditional research peptides. LeadWest covers retatrutide, which is also a GLP-1 class compound, but does not list semaglutide or tirzepatide by name among its supported peptides.
If PeptideDeck only has three inputs, is it missing something important compared to the others?
Not for experienced users. The three inputs, vial mg, BAC water mL, and target dose in mcg, are the only variables the reconstitution formula actually requires. What PeptideDeck skips is the syringe-type selector and the visual guidance that tools like PeptideFox include. For someone already comfortable with the math, that is fine. For a first-time user, the extra context in the other tools is worth the slightly longer workflow.
Sources
- U-100 insulin syringe specifications: FDA device labeling standards, publicly documented
- Peptide dosing unit conventions (mcg vs mg): general pharmacology reference, widely published in compounding literature
- PeptideFox feature descriptions: peptidefox.com, reviewed 2025
- LeadWest Medical calculator peptide list: leadwest.com, reviewed 2025
- MyPeptideMatch compound coverage: mypeptidematch.com, reviewed 2025
