One Rep Max Calculator
Calculate your one-repetition maximum (1RM) and get training percentages for different rep ranges with our free 1RM calculator. Plan your strength training with science-based estimates.
Category: Fitness & Health
Max 15 reps for accurate results
Frequently Asked Questions
What is a one-rep max (1RM)?
A one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It's commonly used in strength training to measure progress, determine training loads, and compare relative strength between individuals.
How accurate is a calculated 1RM?
A calculated 1RM is an estimate based on mathematical formulas and is generally accurate within 5-10% of your actual 1RM. The accuracy decreases when calculating from higher rep ranges (above 10 reps). For the most accurate measurement, a supervised 1RM test with proper warm-up and safety precautions is recommended.
How should I use the percentage-based training weights?
Percentage-based training weights help you plan your workouts based on your 1RM. For strength development, work in the 80-90% range for low reps (1-5). For hypertrophy (muscle building), the 65-80% range for moderate reps (6-12) is often recommended. For endurance, use 50-65% for higher reps (12+). Adjust based on your training goals, experience level, and recovery capacity.
Is it safe to test my actual one-rep max?
Testing a true 1RM carries some risk and should be approached cautiously, especially for beginners. For safety, ensure proper warm-up, use spotters or safety equipment, maintain proper form, and consider working with a qualified strength coach. Many coaches recommend using a calculated 1RM from a 3-5 rep set for safety, especially for recreational lifters.