1RM Calculator (One-Rep Maximum)
Estimate your maximum single lift on bench, squat, or deadlift from a working set using standard Brzycki and Epley formulas.
Calculate your one-rep max (1RM) using validated Brzycki and Epley strength formulas. Get a complete percentage load training chart.
See also: TDEE Calculator (Total Daily Energy Expenditure), Pregnancy Calculator, Proportion Calculator
How it is calculated
Brzycki: 1RM = Weight × [36 ÷ (37 − Reps)]; Epley: 1RM = Weight × (1 + Reps ÷ 30)
Worked example: Bench Press of 100 kg for 5 Repetitions
100 kg lifted for 5 clean repetitions.
- Apply Brzycki formula: 100 × (36 ÷ (37 − 5)) = 100 × (36 ÷ 32) = 112.5 kg.
- Apply Epley formula: 100 × (1 + 5 ÷ 30) = 100 × 1.1667 = 116.7 kg.
- Average both models: (112.5 + 116.7) ÷ 2 = 114.6 kg estimated 1RM.
Estimated 1RM of 114.6 kg.
How to Use This Calculator (Step-by-Step)
- Warm up thoroughly before testing your working set.
- Perform a safe set of 2 to 8 repetitions to technical failure (good form).
- Input the weight and exact completed reps into the calculator.
- Use the generated percentage table to set training weights for your workout cycle.
Frequently asked questions
Why estimate 1RM instead of testing a true single?
Testing a true maximal single carries elevated injury risk to joints and tendons. Submaximal estimation provides safe programming numbers without excessive central nervous system fatigue.
Why do the Brzycki and Epley formulas give different answers?
They are different models of the same set. In the worked example, 100 kilograms for 5 repetitions gives 112.5 kilograms by Brzycki and 116.7 kilograms by Epley, and the calculator averages both models to reach an estimated 114.6 kilograms.
How many repetitions should I use for the best estimate?
Between 2 and 8 repetitions, as the input helper states. Formulas lose accuracy beyond 8 to 10 repetitions, because muscular endurance then matters more than maximal strength.
How do I use the percentage training table?
The how-to steps direct you to use the generated percentage table to set training weights for your workout cycle, so you can train at a chosen percentage of the estimated maximum rather than testing a true single.
Can I enter weight in pounds instead of kilograms?
Yes. The weight input accepts kilograms or pounds, and the estimated maximum comes out in the same unit you entered, so a set entered in pounds gives a maximum in pounds.
What if I completed exactly one repetition?
A completed single repetition is your maximum for that lift by definition. The formulas reflect this: at one repetition the Brzycki factor is exactly one, so the estimated maximum equals the weight lifted.