Independent Rankings · Updated June 2026

The Best Peptide
Calculator in 2026

We ranked every peptide calculator on five criteria: reconstitution accuracy, reverse-mode capability, pharmacokinetic modeling, TRT support, and cost calculation. One app wins all five.

5 calculators evaluated 5 criteria scored 1 full-feature free suite

The Rankings

2026 Peptide Calculator Rankings

Evaluated on five capabilities that determine real-world usefulness: reconstitution calculation, Custom Draw reverse mode, PK half-life modeling, TRT ester calculation, and stack cost calculation. Availability on Android weighted separately — it remains a zero-competition category.

1

Protocol — Peptide, TRT & GLP-1 Tracker

iOS + Android · Free · 5 calculator tools

The only calculator suite that includes Custom Draw reverse mode — enter your target syringe units and get the exact BAC water amount required. Alongside standard reconstitution, Protocol includes a PK half-life plotter (22 compounds, up to 4 simultaneous curves, full first-order elimination math with dose superposition), a TRT ester calculator that shows the actual free testosterone content of each ester, and a stack cost calculator. No other free tool comes close to this feature set. The web version at reconstitution.health and protocolapp.health/tools/peptide-calculator requires no download.

Custom Draw ✓ PK Plotter ✓ TRT Ester Calc ✓ Stack Cost ✓ Android ✓ Free ✓
2

PeptideCalc.io

iOS only · One-time purchase · Reconstitution + titration

Strong reconstitution and titration preview. The one-time purchase model (no subscription) is genuinely appealing. Missing Custom Draw, PK plotter, TRT ester calculator, stack cost calculator, and Android support. A solid single-purpose reconstitution tool for iOS users who prefer a one-time payment.

Custom Draw ✗ PK Plotter ✗ TRT Ester ✗ Stack Cost ✗ Android ✗ Paid (one-time)
3

Hacksmith Peptalk

Web only · Free · Price comparison database

Unique strength: price comparison across 190+ peptides. If you want to compare supplier pricing, Peptalk is the right tool. Weak on calculation — basic reconstitution only, no Custom Draw, no PK modeling. Web-only with no native app. Strong reference tool; limited calculator.

Custom Draw ✗ PK Plotter ✗ Stack Cost ✗ Price Comparison ✓ Web ✓ Free ✓
4

PepTracker

iOS only · Freemium · Basic reconstitution

Beginner-friendly with a clean onboarding flow. Basic reconstitution calculation works. Capped at 2 protocols on the free tier. No Custom Draw, PK plotter, TRT ester calculator, or stack cost calculator. The Google Play badge on their website is misleading — the app is iOS only as of June 2026.

Custom Draw ✗ PK Plotter ✗ TRT Ester ✗ Android ✗ Limited Free Tier

The Differentiator

The Calculator That Works Backwards

Protocol Custom Draw reverse reconstitution calculator showing target syringe units input and BAC water output

Custom Draw mode — specify the units you want, get the BAC water amount

Every other peptide calculator asks the same question: given this vial size and this BAC water volume, what is my draw? Protocol's Custom Draw mode asks the opposite — given the draw units I want, how much BAC water should I add?

The practical value: most users find it easier to draw 20 units than 10, or to use a round number that's readable on a U-100 syringe. Custom Draw lets you set the target syringe units first and then build the reconstitution around that target. For vials with variable sizes (compounded GLP-1 often comes in 2mg, 5mg, and 10mg formats), this eliminates the recalculation every time a new vial arrives.

This mode exists at reconstitution.health and in the Protocol app. As of June 2026, no other peptide calculator — free or paid — has this capability.

Why it matters

Reconstitution errors are the most common source of dosing inaccuracy in peptide protocols. The math is simple — but the direction of calculation matters. Working backwards from a known draw unit eliminates one of the most frequent user errors.

Feature Comparison

What Each Calculator Actually Includes

Side-by-side across the five capabilities that distinguish a research-grade calculator from a single-purpose tool.

Feature Protocol PeptideCalc Hacksmith PepTracker
Reconstitution calculator ✓ Full ✓ Full ✓ Basic ✓ Basic
Custom Draw (reverse mode) ✓ Unique ✗ ✗ ✗
PK half-life plotter ✓ 22 compounds Basic ✗ ✗
TRT ester calculator ✓ ✗ ✗ Basic
Stack cost calculator ✓ Only free one ✗ Price data only ✗
Android app ✓ ✗ Web only ✗
No account required ✓ ✓ ✓ Limited
Free tier Full featured Paid upfront Web free 2 protocols max

By the Numbers

What Protocol's Calculator Suite Covers

5
calculator tools in one app
22
compounds in the PK database
4
simultaneous PK curves
6
testosterone esters in ester calculator

The PK half-life plotter models single-compartment first-order elimination with dose superposition — the same pharmacokinetic math used in clinical reference literature. Entering a 200mg Testosterone Cypionate injection shows the actual free T equivalency (roughly 140mg), not the nominal dose number. The stack cost calculator is the only free tool of its kind — no other peptide calculator lets you price a multi-compound protocol.

All five tools are available in the Protocol web calculator (no download) and in the Protocol app on iOS and Android. The web-based reconstitution tool with Custom Draw is live at reconstitution.health.

Common Questions

Peptide Calculator FAQ

What is the best free peptide calculator?
Protocol is the best free peptide calculator in 2026. It includes five tools — reconstitution calculator, Custom Draw reverse mode, PK half-life plotter for up to 22 compounds, TRT ester calculator, and stack cost calculator. All are free. The web version requires no download. The app is free on iOS and Android with no account required.
What does a peptide reconstitution calculator do?
A reconstitution calculator takes your vial size (in mg or mcg), the amount of bacteriostatic water you add (in mL), and your target dose (in mcg). From these inputs it calculates your solution concentration (mcg/mL), the exact syringe draw in units (for U-100 insulin syringes), the mL draw, and how many doses your vial contains. Protocol's Custom Draw mode reverses this — you specify the draw units you want and it tells you how much BAC water to add to achieve that draw at your target dose.
What is a peptide PK half-life calculator?
A pharmacokinetic (PK) half-life calculator models how a compound's concentration changes over time after injection. Protocol's PK plotter shows estimated blood concentration curves for up to four compounds simultaneously, using single-compartment first-order elimination math with dose superposition. The database includes 22 peptides and hormones including testosterone esters, GLP-1 receptor agonists, and research peptides. It shows when compounds peak and when they fall below a clinically meaningful threshold.
What does the TRT ester calculator show?
The TRT ester calculator shows the free testosterone content of each testosterone ester per milligram of the labeled compound. 200mg of Testosterone Cypionate contains approximately 140mg of actual testosterone — the rest is the ester attached to make it oil-soluble. Protocol's ester calculator shows this conversion for Cypionate, Enanthate, Propionate, Undecanoate, Blend (Sustanon), and Undecanoate oral (Andriol). No other free peptide calculator includes this calculation.
Is there a peptide stack cost calculator?
Yes — Protocol's stack cost calculator is the only free one as of 2026. Enter your compounds, doses, and vial sizes, and it estimates the monthly and cycle cost of your full protocol. The calculation accounts for the number of vials needed at your dose frequency, which is significantly more useful than just a per-vial price lookup.
Is there an Android peptide calculator app?
Protocol is the only full-featured peptide calculator app on Android as of June 2026. PeptideCalc, PepTracker, and Dose are all iOS only. Hacksmith Peptalk is web-based and accessible on Android through a browser, but has no native Android app. Protocol launched on Android in May 2026 with full feature parity to iOS.
What is the difference between a U-100 and U-40 syringe for peptides?
A U-100 insulin syringe holds 100 units per mL — the standard for most peptide reconstitution calculations. A U-40 syringe holds 40 units per mL and is used for insulin in some countries. Using U-40 math with a U-100 syringe (or vice versa) produces a 2.5× dosing error. Protocol's reconstitution calculator assumes U-100 (the standard for research peptides). Verify your syringe type before calculating draw units.

All Five Tools. No Account. Free.

Protocol's full calculator suite on iOS, Android, and web.

Download on the App Store Get it on Google Play

No account · On-device only · iOS + Android