A minimal, installable web app for estimating your one-rep max (1RM) using the Marzagão weight-dependent formula.
Enter a lift, the weight you used, and how many reps you completed — the app estimates the maximum weight you could lift for a single rep. It also generates a percentage breakdown table for planning training intensities.
Three tabs:
- Calculator — enter weight + reps, get an estimated 1RM
- % Table — shows training weights at 50–100% of your estimated 1RM
- My 1RMs — history of saved lifts, persisted in
localStorage
This app uses the Marzagão weight-dependent formula rather than the more common Epley or Brzycki formulas. The key difference: the rep-to-1RM relationship is adjusted based on the actual load, since heavier weights produce a different fatigue curve than lighter ones.
1RM = w × (1 + (r − 1)^0.85 / (−2.55 + 4.58 × ln(w)))
where w = weight lifted and r = reps performed.
The formula is undefined for very low weights (where the denominator approaches zero); the app displays — in those cases.
Accuracy note: Best results come from sets taken close to failure, ideally 3–10 reps. High-rep sets (15+) are less reliable because technique and fatigue become confounding factors before true muscular failure.
| Setting | Options | Default |
|---|---|---|
| Unit | lbs / kg | lbs |
| Display | Round / Exact | Round |
Round mode floors the estimated 1RM to the nearest loadable increment (5 lb or 0.5 kg), so the result is always a weight you can actually put on the bar.
The autocomplete includes ~65 common exercises across squat, hinge, press, row, pull, and isolation patterns. You can type any lift name — it doesn't need to be in the list.
The app ships a web manifest and is installable as a Progressive Web App on both mobile and desktop. On iOS, use Share → Add to Home Screen. On Chrome/Edge, use the install prompt in the address bar.
No build step, no dependencies, no server required — just open index.html.
index.html # App shell and markup
script.js # All logic: formula, state, views, autocomplete
styles.css # Styling
manifest.json # PWA manifest
icon.png # App icon (180×180)
icon.svg # App icon (scalable)