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Your one-rep max (1RM) is the heaviest weight you can lift once with good form. Rather than testing it, you can estimate it from a harder set of several reps.
The calculator averages three well-known formulas and gives a table of weights at different percentages of 1RM for planning workouts.
| Weight lifted | 100 |
| Reps completed | 5 |
| Unit | kg |
| Estimated 1RM | 115.5 kg |
| Epley | 116.7 kg |
| Brzycki | 112.5 kg |
| Lombardi | 117.5 kg |
115.5 kg.
| Weight lifted | 225 |
| Reps completed | 8 |
| Unit | lb |
| Estimated 1RM | 280.4 lb |
| Epley | 285 lb |
| Brzycki | 279.3 lb |
| Lombardi | 277 lb |
280.4 lb.
Lift a weight you can do for 3–8 reps with good form, then use a formula such as Epley: weight × (1 + reps ÷ 30).
Within about 5% for sets of 2–10 reps; less accurate above 12 reps.
About 65–85% for muscle growth (6–12 reps) and 85%+ for strength (1–5 reps).
Only with good technique, a warm-up and a spotter; beginners should use estimates.