🏋️ 1RM (One-Rep Max) Calculator
Calculate your one-rep max (1RM) from weight and number of reps.
What is 1RM?
1RM (One Repetition Maximum) is the maximum weight you can lift for one repetition. It is the standard for setting training intensity.
Testing 1RM directly carries injury risk, so estimation formulas are recommended.
Estimation Formulas
Epley: 1RM = w × (1 + r / 30)
Brzycki: 1RM = w × 36 / (37 - r)
Lombardi: 1RM = w × r⁰·¹
Worked examples
80 kg lifted for 8 reps estimates a 1RM of 80 × (1 + 8 ÷ 30) = 101.3 kg.
100 kg for 3 reps gives 100 × 1.1 = 110 kg, so the same lifter working at 8 reps would use roughly 87 kg.
What the estimate assumes
The formulas are reliable up to about 10 reps; beyond that, technique, endurance and mental tolerance dominate and the estimate overstates the true maximum. Epley and Brzycki disagree by several percent at high rep counts, so treat the number as a training guide. Actual testing needs a thorough warm-up, a spotter and safe rack pins.
Frequently asked questions
- Which formula does the calculator use?
- Epley, 1RM = weight × (1 + reps ÷ 30), which is accurate in the 1–10 rep range. Brzycki gives similar answers below about six reps.
- How do I train at a percentage of my max?
- Multiply the 1RM by the percentage: 75% of 100 kg is 75 kg, typically good for 8–10 reps. Strength work sits at 85–95%, hypertrophy at 67–80%.
- Is it safe to try the estimated max?
- Not straight away. Work up with a 3–5 rep set and add weight gradually, or treat the figure as a ceiling; attempting a true max unprepared risks injury.