One-Rep Max Calculator
Calculate your one-repetition maximum (1RM) for any lift based on the weight and reps you can perform. Use this to plan your strength training program.
Calculate Your One-Rep Max
Enter the weight you can lift and the number of repetitions to estimate your one-rep max.
Understanding One-Rep Max
One-repetition maximum (1RM) is a standard measure of strength in weightlifting and strength training. It represents the maximum amount of weight that you can lift for a single repetition of a given exercise with proper form.
While directly testing your 1RM can be valuable, it also carries risks, especially for beginners or when performed without proper spotting. This calculator uses the Brzycki formula to estimate your 1RM based on the weight you can lift for multiple repetitions, providing a safer alternative to direct testing.
The Brzycki formula: 1RM = Weight × (36 / (37 - Reps))
This formula is most accurate when using a weight that allows you to perform 10 or fewer repetitions. As the repetition count increases beyond 10, the accuracy of the estimation decreases.
Your 1RM is a valuable metric for designing effective strength training programs. By knowing your 1RM, you can calculate appropriate working weights for different training goals:
- Strength Development: 85-95% of 1RM for 1-5 repetitions
- Hypertrophy (Muscle Growth): 67-85% of 1RM for 6-12 repetitions
- Muscular Endurance: 50-67% of 1RM for 12+ repetitions
It's important to note that 1RM can vary between different exercises and muscle groups. For example, your 1RM for bench press will likely differ from your 1RM for squats or deadlifts. Additionally, factors such as technique, fatigue, nutrition, and recovery can all influence your 1RM performance.
For the most accurate results, perform the calculator test when you're well-rested and using proper form. Choose a weight that allows you to complete 2-10 repetitions with good form, and stop the set when you feel you couldn't complete another repetition with proper technique.
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 a common measure of strength in weightlifting and strength training.
- How is one-rep max calculated?
This calculator uses the Brzycki formula: 1RM = Weight × (36 / (37 - Reps)). It estimates your 1RM based on the weight you can lift for multiple repetitions. The formula becomes less accurate beyond 10 repetitions.
- Is it safe to test my actual one-rep max?
Testing your actual 1RM can be risky, especially for beginners or without proper spotting. It puts significant stress on muscles, joints, and connective tissues. Using a calculator to estimate your 1RM is safer and still provides valuable information for training purposes.
- How accurate are one-rep max calculators?
One-rep max calculators provide reasonably accurate estimates, typically within 5-10% of your actual 1RM. Accuracy decreases as repetitions increase beyond 5-10 reps. Different formulas may work better for different individuals and exercises.
- How can I use my one-rep max for training?
Your 1RM can be used to determine appropriate working weights for different training goals. For strength, work at 85-95% of 1RM for 1-5 reps. For hypertrophy (muscle growth), use 67-85% for 6-12 reps. For endurance, use 50-67% for 12+ reps.