[ The problem ]
Most peptide calculators paywall the math. The rest get the math wrong.
13+ peptide calculators ship on the App Store. Most paywall the calculator itself ($4.99–$9.99/mo) — the one piece of math the user actually came for. Reviews are full of the same complaint: "this should be free."
The ones that don't paywall it usually nail one feature and miss the rest — a calc but no log, a log but no library, a library but no reminders, never the four together. And almost none of them visualize the answer. The user does the math in their head, then guesses how far up the syringe to draw.
Meanwhile compounded GLP-1 use has 10×'d in two years. The CDC reported a ~15× rise in poison-control calls for compounded semaglutide and tirzepatide between 2022 and 2023. Most of those calls trace to unit-conversion errors — mg vs mcg vs IU vs mL.
[ The wedge ]
Free, beautiful, accurate. No paywall around the math.
The bet is that a calculator that's faster to use, harder to misread, and doesn't ask for $9.99/mo wins the niche on word-of-mouth. The headline feature is a live, animated syringe that fills to the exact unit mark while you type — so the user is reading a picture, not interpreting a number. Below that: a 25-peptide reference library with cited sources, a 3-tap dose log, vial-level inventory with auto-deplete, schedule + local push reminders, and a vial-recon-date safety alert (no other app does this).
Privacy is the second moat. Stack is local-first by default — anonymous, no account, Face ID lock, screenshot blur in the app switcher, optional stealth icon. Cloud sync is opt-in. The audience cares about this and competitors uniformly default to cloud-first.
Reconstitution calculator
The same math the iOS app uses, embedded here so you can feel it. Pick a peptide, enter your vial size and BAC water, choose a target dose — the syringe fills to the exact unit mark.
Educational tool. Not medical advice. Verify every calculation against your manufacturer or pharmacy label. Consult a licensed healthcare provider before any human use of any compound.
[ Approach ]
Treat the math engine like a contract. Treat the visualization like the headline.
Every numeric operation in the calculator is wrapped in decimal.js. JavaScript's IEEE-754 floats produce different outputs for the same inputs depending on which operation order the code happens to take — fine for a kitchen-scale converter, actively dangerous for a dose calculator. The math layer ships with 30+ unit tests covering the worked examples plus a property test that round-trips any (vial, BAC, syringe, target) tuple back through the formula and asserts <0.01% drift.
The syringe visualization is plain SVG with Reanimated-driven plunger position on the iOS app and a CSS-tweened version on web. Two syringes side-by-side compare U-100 against U-50 so the user sees why the smaller syringe gives more precision at low IU — that one-screen explanation answers more Reddit questions than any FAQ.
[ Feature surface ]
- Reconstitution calculator — forward + reverse, 8 preset peptides, custom mode, save/load named protocols, two-syringe comparison, cost-per-dose math, unit converter (mg ↔ mcg ↔ IU ↔ mL).
- 25-peptide library — mechanism, half-life, dosing range, FDA status, side effects, cycle length, source-cited (FDA labels + PubMed). Filter by goal: recovery, GH, fat loss, cognitive, longevity.
- Dose log — 3-tap log, per-peptide history with chart, weekly grid, adherence stat, optional notes / mood / sleep / energy daily check-in.
- Schedule + reminders — daily / EOD / weekly / 2× daily / custom; local push (no server roundtrip); calendar view; snooze with reason; vial-recon-date alert ("you reconstituted this 28 days ago — replace") that no other app ships.
- Vial inventory — multi-vial per peptide; lot # + recon date + photo; auto-deplete on log; "4 doses left" countdown.
- Privacy — anonymous-first; Face ID app lock; screenshot blur; alternate "stealth" icon; export-and-erase.
- iOS widget — next dose due on the home screen.
[ Stack ]
[ Compliance posture ]
Approval is achievable. The path is documented.
Five live competitor apps — including a Schedule III steroid tracker — name the same compounds and clear App Review with the same playbook: 17+ rating, "educational and personal-tracking" framing, no vendor links anywhere, three-line disclaimer at launch and on every calc / log / library footer, Health & Fitness category (not Medical), local-first storage, no HealthKit write requests in v1.
FDA + Health Canada enforcement in 2026 has been on sellers bundling bac water with peptides — zero actions against information-only apps. The reviewer notes ship pre-baked, citing five precedent App Store IDs by number. Estimated approval probability: 85–93% on first or second submission.
[ Scope ]
Free
Core forever — no paywall on the math
$14.99
One-time IAP — sync, bloodwork, export
25
Peptide reference cards at launch
8 weeks
MVP build — iOS first, Android +30d
[ Status ]
Web demo live. Native app build deferred until Stringer ships.
The full plan suite — PRD, business plan, calculator math spec, App Store regulatory playbook, peptide reference schema, brand direction, 8-week build plan — is locked. The working calculator above is the tech-feasibility proof.
Native iOS build kicks off the week after the prior project (Stringer) launches. Public iOS launch target: mid-October 2026. Android +30 days. This page will update as the app moves from plan to TestFlight to live.