One rep max (1RM) is the heaviest weight you can lift for a single repetition. Testing it directly is risky and demanding, so most programs estimate it from a lighter set — bench 185 lbs for 5 reps and Epley's formula puts the 1RM around 215 lbs. This calculator takes a weight and rep count, runs three standard formulas, and generates a percentage table from 50% to 95% for programming working sets.
How the Three Formulas Compare
- Epley: w × (1 + r/30). Reliable for 3–10 reps; tends to overestimate above 12.
- Brzycki: w / (1.0278 − 0.0278 × r). More conservative, favored for 1–5 reps and used in military fitness standards.
- Lombardi: w × r^0.1. Power-law model that stays reasonable across a wider rep range but can drift high past 15 reps.
Using the Percentage Table
Most structured programs prescribe loads as a percentage of 1RM. A 5/3/1 cycle might call for sets at 65%, 75%, and 85%. Sheiko programs routinely work in the 70%–80% band at higher volumes. The table lets you look up the actual weight for each percentage instead of doing the math mid-session. When a program says '5 × 3 at 80%', you read the number straight off the table.
When to Retest
Reassess every 4–8 weeks, or whenever the prescribed weights feel consistently easy. A single strong session is not a new max — look for a trend over two or three workouts. Beginners gain strength fast enough that monthly retesting makes sense; intermediate lifters can stretch the interval to six weeks or longer.
Accuracy Limits
These formulas were derived from population averages. Individual muscle fiber composition, technique efficiency, and fatigue state all shift the real number. Estimates get less reliable above 12 reps because endurance becomes a bigger factor. Treat the output as a planning tool, not a guarantee — adjust based on how the bar moves.
FAQ
Q: Which formula should I use?
A: If your test set is 5 reps or fewer, Brzycki is usually closest. For 5–10 reps, Epley is the standard. When in doubt, take the average or use the lowest estimate for a conservative training load.
Q: Does this work for squats and deadlifts?
A: Yes. The formulas are lift-agnostic. Keep in mind that squat and deadlift 1RMs are typically higher relative to training weight than bench press, so verify against your actual performance.
Q: Why does the estimate feel too high or too low?
A: Fatigue, sleep, nutrition, and technique all affect the result. If the weight was a grind on the last rep, the estimate may overshoot. If the set felt easy, it may undershoot. Use the estimate as a starting point and adjust.