A 1RM (one rep max) is the maximum amount of weight you can lift for a single repetition with proper form. It's the gold standard for measuring absolute strength and is used to program training percentages for sets and reps.
This calculator uses both the Brzycki and Epley formulas and averages them. Both are accurate within 5% for sets of 1-10 reps. Accuracy decreases with higher rep ranges (10+). For the most accurate result, use a recent set of 3-5 reps.
General benchmarks for men: Beginner 0.5x bodyweight, Intermediate 1x bodyweight, Advanced 1.5x bodyweight, Elite 2x+ bodyweight. For women, roughly 60-70% of those numbers. These vary by age, training history, and body composition.
Tiers here are a bodyweight-ratio ranking for fun; in the app, bosses are HP pools drained by your reps. Every set you log takes a chunk out of the boss's health bar, and bringing it to zero defeats the boss and pays out XP.