10 BAC Water Calculators I Actually Trust for Peptide Reconstitution
Something shifted in 2025 and into 2026. The old method of copying a Reddit thread, doing the math yourself on a napkin, and hoping you got the decimal right stopped being acceptable. More people are working with GLP-1 peptides, tirzepatide, retatrutide, and others where a 10x dosing error is not a minor inconvenience. The tools available have quietly gotten better. Some are still anonymous pages that could disappear tomorrow. A few are genuinely solid. Here are the ten worth bookmarking, ranked by how much I actually trust them.
1. FormBlends Peptide Calculator
This one earns the top spot for a specific reason: it shows the math, not just the answer.
Most tools spit out a number. FormBlends shows you the full calculation so you can sanity-check it yourself. That matters when a 1 mg vs. 1000 mcg confusion can mean drawing ten times your intended dose, which is the single most common error in this space and also the most dangerous one.
The interface is straightforward. You enter the peptide amount in your vial (mg or mcg), the volume of bacteriostatic water you added in mL, and your target dose per injection. It returns the concentration per mL, the exact units to draw on your syringe, and the total number of doses remaining in the vial. It handles the mg-to-mcg conversion automatically. No sign-up required.
It also supports U-100, U-50, and U-40 syringe types, which matters if you are not using a standard U-100 insulin syringe. A visual fill bar shows you exactly where to draw on the syringe barrel, which is more useful than a raw number when you are doing this at 6 a.m. One-tap presets cover common compounds including BPC-157 (5 mg and 10 mg vials), TB-500 5 mg, ipamorelin 10 mg, tesamorelin 2 mg, and GLP-1 class vials around 50 mg.
The tool is built by FormBlends, a company that also operates a 503A compounding pharmacy. That is a real accountability structure. It is not an anonymous landing page.
On mobile, the same calculator lives inside the FormBlends app (iOS and Android). The app adds a 55-compound reference library, a dose log, and an injection-site rotation map. The web tool alone is enough for most people.
One honest note: the calculator does not tell you what dose to take. You enter the dose. It converts that dose into the exact volume you need to draw. That distinction is intentional.
See also: Community Safety Documentation on 84951395589 and Reports
2. PeptideFox
peptidefox.com covers more than 30 peptides and does something clever: it optimizes the BAC water volume suggestion to give you clean unit draws on a U-100 syringe. The visual guide alongside the calculator is genuinely useful for beginners.
3. PeptideDeck
Simple input: mg in vial, mL of BAC water, target dose in mcg. Output: concentration and units to draw, expressed in insulin syringe units. No frills, no account needed.
4. MyPeptideMatch
Free, covers BPC-157, semaglutide, tirzepatide, TB-500, and a handful of other injectables. Good breadth for GLP-1 users specifically.
5. LeadWest Medical Calculator
Includes retatrutide, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, sermorelin, and GHK-Cu in its compound list. Solid mid-range coverage with a clinical-facing presentation.
6. Outliyr Peptide Tool
Covers a similar compound list to LeadWest. BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and GLP-1 class peptides all appear. Useful if you are already on the Outliyr site for other research.
7. peptidereconstitutecalculator.com
BPC-157 specific. If that is the only compound you are working with, it handles the mcg-to-units conversion against a U-100 scale clearly and quickly. Narrow focus, but it does that one thing well.
8. Prime Peptides Calculator
Tied to the Prime Peptides vendor. Functional for basic reconstitution math. Understand that vendor-affiliated tools serve the vendor’s interest first.
9. peptides.org Dosage Charts
Not a calculator. Static reference charts with common dosing ranges for research peptides. Useful for cross-checking numbers, not for doing live reconstitution math.
10. DIY Spreadsheet (Universal Formula)
Any lyophilized peptide follows identical reconstitution math: (dose in mcg / peptide amount in mcg) x BAC water volume in mL x 100 = units to draw on a U-100 syringe. Build it once in Google Sheets and it works forever.
Quick Comparison
| Tool | Free | Sign-up | Syringe Types | Shows Math | App |
| FormBlends Peptide Calculator | Yes | No | U-100/50/40 | Yes | Yes |
| PeptideFox | Yes | No | U-100 | No | No |
| PeptideDeck | Yes | No | U-100 | No | No |
| MyPeptideMatch | Yes | No | U-100 | No | No |
| LeadWest Medical | Yes | No | U-100 | No | No |
| Outliyr | Yes | No | U-100 | No | No |
| peptidereconstitutecalculator.com | Yes | No | U-100 | No | No |
| Prime Peptides Calc | Yes | No | U-100 | No | No |
| peptides.org Charts | Yes | No | N/A | N/A | No |
| DIY Spreadsheet | Yes | No | Any | Yes | No |
FAQ
Why does adding more BAC water change the units I draw but not the dose delivered?
The total peptide in the vial is fixed. If you add 2 mL of water, each mL holds half the peptide. If you add 1 mL, each mL holds all of it. The dose you want stays the same; you just draw a different volume of liquid to get it. More water means more units drawn per dose, not a smaller dose.
What is a U-100 syringe and why does it matter for these calculations?
A U-100 insulin syringe holds 1 mL and marks it as 100 units. So 10 units equals 0.1 mL, 50 units equals 0.5 mL. Most calculators default to U-100. If you are using a U-50 or U-40 syringe, the unit markings mean different volumes and the math changes. Check your syringe type before trusting any output.
Is the reconstitution math different for GLP-1 peptides versus healing peptides like BPC-157?
No. The formula is identical for any lyophilized peptide. The practical difference is scale: BPC-157 and TB-500 are dosed in micrograms (commonly 250-500 mcg), while semaglutide or tirzepatide vials are often in milligrams with doses also in milligrams. Mixing up mg and mcg by a factor of 1000 is the most dangerous error a calculator should catch.
Can I trust a free anonymous web tool with my dosing math?
For verification, yes. Use any reputable tool to check your math. But anonymous pages with no stated owner can disappear, change without notice, or contain unchecked errors. Running the same numbers through two different tools and comparing the outputs takes 90 seconds and catches most mistakes.
Do any of these tools tell me what dose to take?
None of the legitimate ones do. They convert a dose you already have (from a prescriber, a protocol document, or a research plan) into measurable syringe units. Deciding the dose is a separate question that belongs with a qualified medical provider.
Sources
- U-100 insulin syringe volume standards: FDA labeling conventions for insulin syringes
- Peptide reconstitution math: standard compounding pharmacy calculations (concentration = mass/volume)
- PeptideFox compound list: peptidefox.com (publicly viewable, 2026)
- MyPeptideMatch compound list: mypeptidematch.com (publicly viewable, 2026)
- LeadWest Medical calculator: leadwestmedical.com (publicly viewable, 2026)
- Outliyr peptide tool: outliyr.com (publicly viewable, 2026)
- FormBlends Peptide Calculator features: formblends.com web tool and app store listings (publicly viewable, 2026)