🏋️ One Rep Max (1RM) Calculator
Estimate your one-rep max from any set of 1–12 reps, plus a percentage chart for planning training weights.
How the One Rep Max (1RM) Calculator Works
Your one-rep max (1RM) is the heaviest weight you can lift once with good form. Testing it directly is demanding and carries more risk, so lifters usually estimate it from a lighter set taken close to failure. Enter the weight you lifted and the number of clean reps you completed, and the calculator applies three established formulas — Epley, Brzycki, and Lombardi — and averages them.
Estimates are most reliable for sets of about 10 reps or fewer, which is why input is limited to 12 reps. The percentage chart shows typical training weights at each intensity. Weight units do not matter: enter kilograms or pounds and the results are in the same unit.
Formula
Epley: 1RM = w × (1 + r / 30) Brzycki: 1RM = w × 36 / (37 − r) Lombardi: 1RM = w × r^0.10 w = weight lifted, r = repetitions completed
How to Use It
- Enter the weight you lifted (kg or lb).
- Enter how many clean reps you completed (1–12).
- Read your estimated 1RM and use the chart to plan training sets.
Frequently Asked Questions
How do I calculate my one rep max?
Lift a weight you can manage for roughly 3–10 clean reps, then plug the weight and reps into a formula such as Epley: 1RM = weight × (1 + reps ÷ 30). For 100 kg × 5 reps, Epley gives about 117 kg.
Which 1RM formula is most accurate?
No single formula is best for everyone or every lift. They agree closely at low rep counts and diverge as reps increase, so averaging several formulas — as this calculator does — gives a balanced estimate.
Should I test my true 1RM?
It is not necessary for most people. Estimated 1RMs are accurate enough to plan training, and they avoid the fatigue and injury risk of maximal attempts. If you do test, use a spotter and proper warm-up.
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Formula and content last reviewed: September 2026. All calculations run in your browser — nothing you enter is sent to or stored on our servers.
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See all →✔ Reviewed by GelirLab Editöryal Ekibi · Last reviewed: September 2026 · How we check our calculators