One-Rep Max Calculator
Estimate 1RM with Epley, Brzycki and Lombardi formulas.
Overview
A one-rep max (1RM) is the heaviest load a lifter can move for a single repetition with proper form. Testing it directly is risky and fatiguing, so coaches almost always estimate 1RM from a submaximal set — for example, five reps with a moderately heavy bar — using a small set of well-known regression formulas. The estimate then anchors percentage-based programming for strength, hypertrophy, and power phases.
This calculator shows the Epley, Brzycki, and Lombardi estimates side by side. They agree closely at low rep counts and drift apart above eight to ten reps, where the relationship between reps and load becomes more individual. Seeing all three lets you triangulate a working number without overfitting to any single equation.
How it works
- Epley (1985):
1RM = weight × (1 + reps / 30). - Brzycki (1993):
1RM = weight × 36 / (37 − reps). - Lombardi (1989):
1RM = weight × reps ^ 0.10.
All three are empirical fits and should be trusted most when the test set is between two and six repetitions to true failure. Above that, the formulas overshoot because higher-rep work also depends on muscular endurance and cardiovascular factors, not just maximum strength. Below two reps the estimate is essentially the lifted weight itself.
Once 1RM is known, training programmes typically prescribe 65–75% of 1RM for hypertrophy, 80–90% for pure strength, and 90%+ for peaking. The estimate is also used to plot a velocity-loss or RPE-based load when bar speed sensors are not available.
Examples
- Bench press 100 kg for five reps. Epley: 117 kg; Brzycki: 113 kg; Lombardi: 117 kg. Working 1RM around 115 kg.
- Squat 140 kg for three reps. Epley: 154 kg; Brzycki: 154 kg; Lombardi: 156 kg. Consistent estimate near 155 kg.
- Deadlift 180 kg for one rep — all three formulas return 180 kg.
- Overhead press 60 kg for eight reps. Epley: 76 kg; Brzycki: 75 kg; Lombardi: 75 kg. Less reliable due to the rep count.
FAQ
Should I ever test a real 1RM?
Maybe, sparingly, for competitive lifters. For most trainees an estimate from a clean set of three to five is safer and just as useful.
Which formula should I trust?
At low reps, all three. At higher reps, Brzycki tends to be slightly more conservative.
Does technique failure count?
No — only repetitions completed with sound form. Counting grindy partial reps inflates the estimate dangerously.
Why does my real 1RM differ from the estimate?
Neural adaptations, technique, and grip on the day all influence single-rep performance more than multi-rep work.