What is a one-rep max (1RM)?

A one-rep max (1RM) represents the absolute maximum weight you can lift for a single repetition of an exercise while maintaining proper form. It is the gold standard for measuring your maximal strength in weightlifting and is a key metric for designing effective training programs.

Why shouldn't I just test my true 1RM instead of calculating it?

Testing a true 1RM is physically and neurologically exhaustive. It carries a significantly higher risk of injury, especially for beginners or those training without an experienced spotter. Using a 1RM calculator based on a submaximal lift (e.g., a 5-rep or 8-rep set) is a much safer, time-efficient, and still highly effective way to estimate your maximal strength for programming purposes.

How accurate is this 1RM calculator?

This calculator's accuracy is very high because it averages the results from seven different scientifically validated formulas. The estimations are most reliable for lifts performed in the 2-10 repetition range. By providing a range of estimates, it gives a comprehensive view of your likely true max, accounting for variations in individual leverage, muscle fiber type, and training experience.

Which 1RM formula is the best?

There is no single 'best' formula for everyone. The Brzycki formula is widely used and considered very reliable for most lifters. The Epley formula is another popular and accurate choice. However, accuracy can vary based on the individual and the exercise. That's why this calculator provides an average of seven formulas, giving you a more balanced and practical estimate of your true strength.

One Rep Max (1RM) Calculator

Instantly estimate your true strength for any lift. Use our free, accurate 1RM calculator to guide your training and break new personal records.

Weight Lifted

Repetitions

Units

Your Estimated One-Rep Max is:

1RM Estimates by Formula

Training Percentages

% of 1RM	Weight	Est. Reps

Unlock Your True Strength with the 1RM Calculator

Your one-repetition maximum, or 1RM, is the single most important measure of your maximal strength. It's the absolute heaviest weight you can lift for one complete repetition of an exercise with proper form. Knowing your 1RM is the key to unlocking smarter, more effective training. It allows you to move beyond guesswork and structure a program that precisely targets your goals, whether it's building muscle, gaining pure strength, or improving endurance.

A Simple Guide: How to Use the 1RM Calculator

Instead of risking injury with a dangerous max-out attempt, you can find your estimated 1RM in just a few safe and easy steps.

Warm-Up Thoroughly: Prepare your body for the specific lift you're testing (e.g., squat, bench press, deadlift) with several lighter sets, gradually increasing the weight.
Perform Your Test Set: Choose a challenging weight you believe you can lift for 5 to 10 reps. Perform one set to near-failure, meaning you stop when you feel you only have 1-2 good reps left in the tank. The accuracy of the calculation is highest in this rep range.
Enter Your Numbers: Input the weight you lifted and the number of reps you successfully completed into the calculator above.
Get Your Results: Click "Calculate" to see your estimated 1RM. Our tool provides an average from seven scientific formulas, giving you the most reliable strength estimate possible.

Which 1RM Formula is Best? A Quick Comparison

You'll notice our calculator provides results from several formulas. While all are scientifically validated, they have slight differences. Here's a quick look:

Brzycki & Epley: These are the two most popular and widely trusted formulas in the fitness industry. For most people, these provide a very accurate estimate.
Lander, Lombardi, Mayhew, O'Conner, Wathan: These other formulas use different mathematical models. By averaging all seven, our calculator smooths out any outliers and gives you a practical, actionable number to use for your training.

For 99% of lifters, the average result shown at the top is the best number to use for programming your workouts.

How to Train Using Your 1RM Percentages

Percentage-based training is a proven method to guarantee progress. Once you have your 1RM, structure your workouts using these zones:

Pure Strength: Train with 90-100% of your 1RM for sets of 1-3 reps. This builds raw strength and power.
Hypertrophy (Muscle Growth): The "sweet spot" for building muscle size is 70-85% of your 1RM, typically performed for 6-12 reps per set.
Muscular Endurance: To improve your muscles' ability to work for longer periods, use 50-65% of your 1RM for sets of 15 reps or more.

Remember that consistent training and proper nutrition are essential for progress. To dial in your diet, use our Macro Calculator to ensure you're consuming enough protein and calories to fuel muscle recovery and growth.