My first peptide vial sat on the counter for two days because I could not figure out whether to draw 10 units or 100. Same dose, completely different number depending on how much water I had added. That confusion is exactly where dosing errors happen, and it is where a good reconstitution calculator earns its keep.
Here are eight tools I looked at, ranked honestly.
1. FormBlends Peptide Calculator
Verdict: The one I’d hand to a first-timer without hesitation.
The single fact that separates this from every other tool on this list: it shows you the math, not just the answer. You can see the concentration formula working in real time. That matters when you are about to inject something into your body.
Enter your vial size (in mg or mcg), the mL of bacteriostatic water you added, and your target dose. It outputs the exact insulin syringe units to draw, the concentration per mL, and the total number of doses left in the vial. It handles the mg-to-mcg conversion automatically, which is the 1000x mistake that causes real harm. A visual syringe bar shows exactly where the plunger should sit.
It defaults to U-100 syringes but also supports U-50 and U-40. One-tap presets cover BPC-157 at 5mg and 10mg, TB-500, ipamorelin, tesamorelin, and GLP-1 class compounds. No account required. Works on any browser. Also lives inside the FormBlends mobile app alongside a 55-compound library and an injection-site rotation tracker.
Built by a real 503A pharmacy company rather than an anonymous webpage. That accountability matters when every other option on this list is effectively authorless.
2. PeptideFox
Verdict: Best visual aid for syringe-shy beginners.
PeptideFox (peptidefox.com) covers 30-plus peptides and does something most calculators skip: it optimizes your BAC water volume recommendation to produce clean, whole-unit draws on a U-100 syringe. Fewer awkward 7.3-unit draws. It also includes a visual guide showing the syringe markings. Good supplementary reference.
3. PeptideDeck
Verdict: Bare-bones but it does the core math correctly.
Enter your peptide amount in mg, the water added in mL, and your target dose in mcg. PeptideDeck returns the resulting concentration alongside the exact volume to draw, expressed as both a decimal mL figure and an insulin unit count. No presets. No frills. I appreciate that it keeps the interface honest about what it is: a calculator, not a protocol generator.
4. MyPeptideMatch
Verdict: Useful if you are working with GLP-1 class compounds specifically.
Free, no login. Covers BPC-157, semaglutide, tirzepatide, TB-500, and a handful of other injectables. The semaglutide and tirzepatide support makes it worth bookmarking separately from any healing-peptide calculator, since GLP-1 dosing conventions differ enough to warrant their own reference.
*(Quick honest aside: none of these tools, including the top pick, replace a prescription or a conversation with a licensed prescriber. They measure. That is all.)*
5. LeadWest Medical Calculator
Verdict: Good compound coverage for a clinical-adjacent audience.
LeadWest Medical’s calculator handles retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu. That retatrutide inclusion is notable because few free tools have caught up to it. The interface is straightforward and appears tied to an actual medical practice, which gives it more standing than a random GitHub page.
6. Outliyr Peptide Calculator
Verdict: Solid overlap with LeadWest, slight edge in GLP-1 framing.
Outliyr covers BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class peptides. The content around each compound leans toward the biohacking reader. Functional calculator. Worth cross-referencing if you are working with two peptides simultaneously and want a second opinion on concentration math.
7. peptidereconstitutecalculator.com
Verdict: BPC-157 only, but very clear for that one compound.
Narrow scope. If BPC-157 is your only focus, the mcg-to-U-100-units conversion here is clearly explained and accurate. Not useful beyond that single compound. No identified author or company. Use it as a spot-check, not a primary tool.
8. peptides.org Dosage Charts
Verdict: Reference material, not a live calculator.
Static charts rather than an interactive tool. Useful for sanity-checking whether your provider-assigned dose is in a normal range for a given compound. Because the reconstitution math is identical for any lyophilized peptide, peptides.org works best as context, not as a step-by-step guide for drawing a syringe.
A Note on All Free Web Tools
Most of these pages have no company, no contact page, and no update history. The universal math is simple (dose divided by concentration equals draw volume) and it does not change, so accuracy is rarely the issue. Accountability is.
Common Questions
Does it matter which reconstitution calculator I use, or is the math always the same?
The underlying formula never changes: dose divided by concentration equals draw volume. What differs is whether a tool handles unit conversions for you, flags the mg-to-mcg shift automatically, and supports your specific syringe type. FormBlends does all three. A bare-bones tool like PeptideDeck does the arithmetic correctly but leaves unit-conversion awareness entirely to you.
Why does FormBlends show U-50 and U-40 options when most peptide users only own U-100 syringes?
U-100 is the standard, but U-50 and U-40 syringes still circulate in some countries and older supply chains. If you draw using the wrong syringe scale, your actual dose is off by a factor of two or more. Supporting all three types means the calculator stays accurate regardless of what the user has on hand.
PeptideFox recommends a specific BAC water volume rather than just accepting whatever I enter. Is that actually useful?
Yes, for a practical reason. Adding a volume that produces an awkward concentration, say 7.3 units per dose on a U-100 syringe, makes accurate drawing harder. PeptideFox back-calculates the water amount that lands on a clean whole unit. That is a small thing that meaningfully reduces drawing errors over a multi-week protocol.
Can I use peptidereconstitutecalculator.com for semaglutide or tirzepatide, or is it genuinely limited to BPC-157?
Genuinely limited. The site addresses only BPC-157 reconstitution. For GLP-1 class compounds like semaglutide and tirzepatide, MyPeptideMatch is the free tool on this list specifically built around those dosing conventions. Using a BPC-157-focused calculator for a GLP-1 compound is not dangerous on its own, but the dose framing and typical concentration ranges differ enough to cause confusion.
None of these tools ask for my body weight. Should a reconstitution calculator factor that in?
No, and that is intentional. Reconstitution calculators solve one problem: how many syringe units to draw given a vial concentration and a target dose in mcg or mg. Weight-based dosing is a prescriber decision made before you ever open the calculator. If your protocol already specifies a fixed mcg dose, body weight is irrelevant to the drawing math.
Sources
- U.S. FDA: guidance on insulin syringe unit standards (U-100, U-50, U-40 definitions)
- peptides.org: publicly accessible peptide dosage reference charts
- peptidefox.com: tool documentation and peptide support list
- FormBlends web tool: feature descriptions drawn from direct tool inspection
