Three jobs, and who does which
People on a peptide protocol are doing three separate things: smoothing a noisy weight series, logging injections, and working out concentrations. Almost every app does one.
The pattern below is structural rather than a knock on any one product. The high-volume GLP-1 trackers log injections well and rotate sites, and none of them advertises named trend smoothing or reconstitution maths. The serious smoothing apps do real trend mathematics, and none of them advertises injection logging. The peptide calculators do reconstitution, and none names a smoothing algorithm.
Peptrend sits across all three, which is the honest claim and the only one worth making. It is not the best of them at every job, and where another app is the better answer this page says so.
| App | Lane | Smoothing method named | Dose log | Site rotation | Reconstitution | Platform |
|---|---|---|---|---|---|---|
| Apple Health | built-in baseline | no — bucketed weekly, monthly and yearly views | no | — | no | iPhone, iPad; built in, free |
| Happy Scale | smoothing | four named; the default’s formula is not published | not advertised | — | not advertised | iPhone, iPad, Mac |
| TrendWeight | smoothing | ESMA, α = 0.1, published in full | not advertised | — | not advertised | web only; weigh-ins typed in or synced from Withings |
| Libra | smoothing | time-weighted EWMA, formula published | not advertised | — | not advertised | iPhone, Android |
| MacroFactor | smoothing | not named | not advertised | — | not advertised | iPhone, iPad, Apple Watch, Android; no free tier |
| Shotsy | GLP-1 tracker | not named | yes | visual map, reads your history | not advertised | iPhone |
| GlucoPal (listed as “Zepbound & Mounjaro Tracker”) | GLP-1 tracker | not named — "weekly averages" | yes | automatic rotation map | not advertised | iPhone |
| PeptidePal | peptide | not advertised | yes | interactive body map, heat-mapped | yes, shown on a syringe diagram | iPhone |
| Peptide Tracker & Calculator | peptide | not advertised | yes | site map with rest periods | yes | iPhone, iPad |
| PepCalc | peptide | not advertised | — | — | yes | iPhone, iPad; one-time purchase |
| Peptrend | all three | fifteen, parameters published for each | yes | round-robin by dose count | strength ÷ water = mg/mL | iPhone, iPad |
Where another app is the better answer
If you are not injecting anything and only want a smoothed line, Happy Scaleanswers the question on iPhone with a large user base behind it, and Libra does the same across iOS and Android with its formula published.
If you want the maths open and the price zero, TrendWeight is free, open source and documents its α, its rate window, its interpolation rule and its calorie constant. It sets the ceiling on explainability in this category, and matching that standard is why Peptrend publishes all fifteen of its own methods. It is web-only: weigh-ins are typed into the site or synced from a Withings account, and its FAQ says Fitbit syncing is expected to stop in September 2026.
If you want a single-purpose injection log with a mature site map and no interest in trend mathematics, Shotsy is the established option in that lane.
What Peptrend adds
Named smoothing beside a dose log. Fifteen methods with every parameter published, including four lifted from technical analysis and a constant-velocity Kalman filter, share a timeline with the doses, a decayed-milligram estimate of what is left from the last one, and a reconstitution screen that reports concentration and deliberately refuses to compute a dose or a draw volume. No other app in the table advertises named smoothing and a dose log together.
Holding both series also lets the weekly progress chart take its colour from the dose taken that week, so a titration ladder shows up in the weight data. That is no longer Peptrend’s alone: Shotsy’s App Store listing now advertises “color-coded weight charts by dose” as well.
On prices
This page quotes none, and that is deliberate. App Store in-app-purchase panels list promotional, regional and A/B-test SKUs rather than the offer any individual user is shown — one app in the table above lists five different subscription SKUs, another nine. Any figure written here would be wrong for most readers within a month. Check each listing. Peptrend’s own tiers are on the home page and on its App Store listing, which is the only authority worth quoting for any of these apps.
How this was compiled
Each row was read from that app’s own published listing on 18 September 2026, not from installing and driving it. That is why absences are written as “not advertised” rather than as statements about what an app can do. Each app's own listing is the authority, and it is the thing to check before relying on any row here.
The longer version, with review counts, lineage and the mathematics behind each named method, is in the full comparison.