1-Rep Max Calculator

How to Use This Calculator

Enter the weight you just lifted and the number of reps you performed to failure (i.e., you could not do another rep with good form). The calculator will estimate your one-rep maximum using both the Epley and Brzycki formulas, then average them to provide a robust estimate. You'll also see your training zones for strength, hypertrophy, and endurance based on standard percentages of your 1RM.

Formula and Methodology

The Epley formula is: 1RM = Weight × (1 + Reps/30). The Brzycki formula is: 1RM = Weight × (36/(37 - Reps)). Both are validated for reps between 1 and 12. We average them to counteract individual variation. For example, if you lift 100kg for 5 reps, Epley gives 116.7kg, Brzycki gives 112.5kg, so the estimate is about 114.6kg.

Practical Examples

Example 1: Bench press 80kg for 8 reps. Epley: 80×(1+8/30)=101.3kg, Brzycki: 80×(36/29)=99.3kg, average = 100.3kg. Your training zones would be: strength 85-95% = 85-95kg, hypertrophy 67-85% = 67-85kg, endurance 55-67% = 55-67kg.

Example 2: Squat 140kg for 3 reps. Epley: 140×(1+3/30)=154kg, Brzycki: 140×(36/34)=148.2kg, average = 151.1kg. This shows how fewer reps give a higher per-rep efficiency.

Tips and Best Practices

Always use a spotter or safety equipment when testing to failure. For beginners, stick to 3-5 reps for safety. Update your 1RM estimate monthly to keep your training zones accurate. Use the deload load (50% of 1RM) during recovery weeks to reduce fatigue while maintaining movement patterns. Periodize your training by alternating between strength, hypertrophy, and endurance blocks based on the zones shown.