1RM: One Rep Maximum Calculator

About the One-Rep Max Tool

This One-Rep Max (1RM) Calculator helps you estimate the maximum amount of weight you can lift for a single repetition of any given exercise — based on how much weight you used and how many reps you completed.

It uses the Landers Formula, introduced in 1985 in the NSCA Journal, a trusted and widely accepted method in strength training science. The formula is:

1RM = (100 × Weight Lifted) / (101.3 − 2.67123 × Reps)

Here’s how it works:

• You perform an exercise set to near failure — lifting a challenging weight for as many reps as possible with good form.
• Enter the weight and number of reps into the calculator.
• We’ll estimate your 1RM and show common training intensities from 55% to 95%, helping you target specific goals like endurance, hypertrophy, or strength.

Important Safety Reminder:
Never test your one-rep max without supervision. Attempting a true 1RM lift without a spotter can be extremely dangerous. If you're going to push to failure, always train with a partner — ideally, one on each side of the bar.

Whether you're programming your next strength phase or simply curious about your potential, this tool gives you a smart and practical way to personalize your workouts — all based on what you're already doing in the gym.

Scientific Reference:
Landers J. Maximum based on reps. NSCA Journal, 1985.