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

Your one-repetition maximum (1RM) is the absolute most weight you can lift for a single repetition of a given exercise with proper form. It is the gold standard for measuring your maximal strength. While performing a true 1RM test can be effective, it also carries a high risk of injury. This calculator allows you to safely *estimate* your 1RM based on a weight you lifted for multiple repetitions.

Why is Calculating Your 1RM Important?

Your 1RM is one of the most valuable numbers in strength training. It allows you to program your workouts with precision using a method called percentage-based training. By training with specific percentages of your 1RM, you can target different goals:

• Maximal Strength: Typically trained at 90-100% of 1RM for 1-3 reps.
• Hypertrophy (Muscle Growth): Best stimulated at 70-85% of 1RM for 6-12 reps.
• Muscular Endurance: Developed using lighter loads, around 50-65% of 1RM for 15+ reps.

Tracking your estimated 1RM over time is also a fantastic way to measure progress without having to perform dangerous, maximal lifts frequently. As your strength increases, so will your body's Lean Body Mass, which is a key component of a healthy body composition.

The Formulas Used

There is no single, perfect formula for estimating 1RM. This calculator provides seven popular and scientifically validated equations. The **Brzycki** and **Epley** formulas are the most widely used. Different formulas may give slightly different results, especially at higher rep ranges (>10), where estimations become less accurate.

How to Use the Results Table

Once your 1RM is calculated, use the table above to plan your workouts. For example, if your goal is muscle growth and the table says your 75% lift is 150 lbs, you should aim to perform your sets with 150 lbs for the target rep range (e.g., 8-10 reps). Fuelling this type of training requires adequate energy, which you can plan for using our Calorie Calculator.

Safety Warning: An estimated 1RM is not the same as a true 1RM. Always prioritize proper form, use a spotter when lifting heavy, and listen to your body to prevent injury.