One-Rep Max (1RM) Calculator

Estimate Your True Strength

Your one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. It's a key metric for structuring strength training programs and tracking progress. This calculator uses the popular Brzycki formula to estimate your 1RM without you having to perform a risky maximal lift.

The 1RM Formula Explained

There are several formulas to estimate 1RM, but the Brzycki formula is one of the most common: 1RM = Weight Lifted / (1.0278 - (0.0278 * Repetitions))

• This formula is most accurate for repetition counts of 10 or less.

How to Use the Calculator

1. Weight Lifted: Enter the weight you used for a challenging set.
2. Repetitions: Enter the number of reps you successfully completed with that weight.
3. Calculate 1RM: The tool will provide your estimated one-rep max.

Real-World Example

You perform a bench press set where you successfully lift 185 lbs for 5 repetitions.

• Weight: 185
• Reps: 5
• Calculation: 1RM = 185 / (1.0278 - (0.0278 * 5)) = 185 / 0.8888 ≈ 208 lbs.
• Your estimated one-rep max for the bench press is 208 lbs.

Frequently Asked Questions (FAQ)

• Why estimate 1RM instead of just testing it? Testing your true 1RM is physically demanding and carries a higher risk of injury, especially for inexperienced lifters. Estimating it from a sub-maximal set (like 3-5 reps) is much safer.
• How can I use my 1RM in my training? Your 1RM is used to calculate percentages for your workouts. For example:
  • Strength Training: Work in the 80-90% of 1RM range (e.g., 3-5 reps).
  • Hypertrophy (Muscle Growth): Work in the 65-80% of 1RM range (e.g., 8-12 reps).
  • Endurance: Work in the 50-65% of 1RM range (e.g., 15+ reps).
• Is this formula 100% accurate? No, it's an estimate. Individual factors like muscle fiber type and exercise technique can affect your true 1RM. However, it provides a very useful and consistent baseline for programming your training.