What is a One-Rep Max (1RM)?

A one-repetition maximum (1RM) is the heaviest weight you can lift for a single repetition of a given exercise with proper form. It is a common measure of strength in weight training, particularly for core lifts like the squat, bench press, and deadlift. While finding your true 1RM by lifting maximal weight can be effective, it is also physically demanding and carries a higher risk of injury. This calculator provides a safe and reliable way to estimate your 1RM without needing to perform a maximal lift.

How to Use the Calculator

To estimate your 1RM, perform a set of a specific exercise to muscular failure (meaning you could not complete another rep with good form). Then enter the following:

• Weight Lifted: The total weight you used for that set.
• Repetitions Performed: The number of successful repetitions you completed. This calculator is most accurate for reps between 2 and 10.

The Brzycki Formula

This calculator uses the Brzycki formula, one of the most common and validated equations for estimating 1RM. The formula is:

1RM = Weight / (1.0278 - (0.0278 * Repetitions))

This method is widely used because it provides a reliable estimate, especially when using a weight that allows you to perform 10 or fewer repetitions.

Why Calculate Your 1RM?

Knowing your 1RM can be incredibly useful for structuring your training. Many strength training programs are based on percentages of your 1RM. This is a concept called percentage-based training. For example, a program might instruct you to perform:

• Strength: 5 sets of 5 reps at 85% of your 1RM.
• Hypertrophy (Muscle Growth): 3 sets of 8-12 reps at 70-80% of your 1RM.
• Endurance: 3 sets of 15+ reps at 50-60% of your 1RM.

By using your calculated 1RM, you can determine the exact weight to use for each workout, ensuring you are training with the right intensity to meet your goals and make consistent progress.

Disclaimer: This calculator provides an estimate of your 1RM. Your actual one-rep max may be slightly different. Always prioritize proper form and safety. When attempting a true maximal lift, it is highly recommended to do so with an experienced spotter.