Estimate your one-rep max from submaximal lift data
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise with proper form. It is the gold standard for measuring absolute strength and is widely used to programme training intensity -- most strength programmes prescribe weights as a percentage of your 1RM (e.g. "5 sets of 5 at 75% 1RM"). Testing a true 1RM involves progressively loading a barbell until you reach the heaviest weight you can complete one rep with. However, this carries a higher risk of injury, especially for beginners or those training alone. A safer and equally practical approach is to estimate your 1RM from a submaximal set -- for example, the heaviest weight you can lift for 3-5 reps. This calculator uses two well-validated formulas (Epley and Brzycki) to estimate your 1RM from any submaximal set of up to 15 reps. Both formulas produce similar results and the average provides a reliable working estimate for programming purposes.
To estimate your one-rep max: 1. Enter the weight you lifted in kilograms. Use a weight you can complete with good form -- a sloppy or partial rep will give an inaccurate estimate. 2. Enter the number of repetitions you completed. For the most accurate result, use a set of 3-5 reps. Accuracy decreases above 10 reps. 3. Review your results. The calculator shows estimates from both the Epley and Brzycki formulas, along with their average. Use the average as your working 1RM for programming. 4. Apply to your training. Common training zones based on 1RM: strength (85-100%), hypertrophy (65-85%), endurance (50-65%). Important: Never attempt a true 1RM without a competent spotter and proper warm-up. Submaximal estimation is safer and nearly as accurate for training purposes.
This calculator uses two established 1RM estimation formulas: **Epley Formula (1985):** 1RM = weight x (1 + reps / 30) **Brzycki Formula (1993):** 1RM = weight x (36 / (37 - reps)) Both formulas are regression-based, derived from large datasets of actual 1RM tests. They are most accurate for 1-6 reps and become progressively less reliable above 10 reps. For example, if you lift 100 kg for 5 reps: - Epley: 100 x (1 + 5/30) = 100 x 1.167 = 117 kg - Brzycki: 100 x (36/32) = 100 x 1.125 = 113 kg - Average: 115 kg The Brzycki formula tends to be slightly more conservative. At very high rep ranges (12-15), the Epley formula may overestimate. The average of both provides a practical middle ground.
These formulas apply to compound barbell exercises such as the squat, bench press, deadlift, and overhead press. They may be less accurate for isolation exercises or machine-based movements. Individual variation in muscle fibre composition means some people are naturally better at high reps relative to their 1RM, and vice versa. Treat the estimate as a starting point and adjust based on your training experience.