One-Rep Max (1RM) Calculator
Your one-rep max (1RM) is the heaviest weight you can lift once for a given exercise. Testing it directly is risky, so it is usually estimated from a weight you can lift for several reps. The Epley formula is the most common estimator.
Enter the weight you lifted and the number of reps (up to about 10). The calculator returns your estimated 1RM and percentages for common training intensities.
It lets you programme training loads as a percentage of your max without testing that max every session — useful for any structured strength programme.
Enter your values to see the result.
How this is calculated
Your one-rep max (1RM) is the heaviest weight you can lift once for a given exercise. Testing it directly is risky, so it is usually estimated from a weight you can lift for several reps. This calculator uses the Epley formula: 1RM = weight × (1 + reps ÷ 30), where weight is the load you lifted and reps is the number of repetitions you performed with it.
The calculator also reports common training intensities as percentages of the estimated 1RM — 85% for the 5-rep range and 70% for the 8–12 rep range — so you can set loads for a programme without maxing out each time.
The Epley formula is most accurate for reps under about 10; beyond that, fatigue makes the estimate less reliable, and different formulas (Brzycki, Lombardi) give somewhat different numbers. The model does not account for exercise-specific differences (leg press 1RM estimates differently from bench press), individual variation in fatigue resistance, or form breakdown. An estimate is a guide, not a guarantee — if you ever test a true max, warm up thoroughly and use a spotter or safety pins.
Worked example
You lifted 80 kg for 5 reps on the bench press.
- 11RM = 80 × (1 + 5 ÷ 30) = 80 × 1.1667 ≈ 93.3 kg.
- 285% (5-rep range) = 93.3 × 0.85 ≈ 79.3 kg.
- 370% (8–12 rep range) = 93.3 × 0.70 ≈ 65.3 kg.
Frequently asked questions
- What is the Epley formula?
- 1RM = weight × (1 + reps/30). It is most accurate for reps under about 10; beyond that, fatigue makes the estimate less reliable.
- Why use percentages of 1RM?
- Training programmes prescribe intensity as a percentage of 1RM — e.g. 5 reps at 85%. Knowing your 1RM lets you set those loads without maxing out each session.
- Is an estimated 1RM safe to attempt?
- An estimate is a guide, not a guarantee. If you test a true max, warm up thoroughly, use a spotter or safety pins, and stop if form breaks down.
- What is the Epley formula?
- 1RM = weight × (1 + reps ÷ 30). It is most accurate for reps under about 10; beyond that, fatigue makes the estimate less reliable, and other formulas give slightly different numbers.
- Is an estimated 1RM safe to attempt?
- An estimate is a guide, not a guarantee. If you test a true max, warm up thoroughly, use a spotter or safety pins, and stop if form breaks down. Most programmes use percentages of the estimate rather than testing the true max regularly.
Related calculators
Method: Epley one-rep-max estimation formula. No external data source. Last updated: September 2026.
These results are general estimates from established formulas and are not medical advice. They depend on the accuracy of the values you enter and on individual factors the formulas cannot capture. Consult a qualified healthcare professional before making decisions about your diet, training or treatment.