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1RM Calculator

Calculate your one-rep max (1RM) for any exercise with perceived exertion adjustment

kg

10 = Maximum effort | 8 = Moderate effort | 5 = Low effort

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How does the 1RM calculator work?

The 1RM calculator allows you to calculate your one-rep max (1RM) without having to lift the maximum weight. You only need to enter the weight lifted, repetitions completed, and RPE (rate of perceived exertion). The 1RM calculation uses the most accurate formulas: Epley and Mayhew, and adjusts according to your effort level to give you the most accurate result possible.

How to use the 1RM calculation?

Select the formula you prefer (Epley is the most popular, Mayhew is the most scientific). Enter the weight you lifted, the repetitions completed, and the RPE (0-10) indicating how much effort it took. RPE 10 means you reached total failure, 9 means you could do 1 more rep, 8 means you could do 2 more, etc. The calculator will adjust your 1RM based on this data.

Formulas used

Epley

1RM = peso × (1 + reps / 30)

The most popular and accurate. Works 99% of the time. Ideal for 1-10 repetitions.

Mayhew

1RM = (100 × peso) / (52.2 + 41.9 × e^(-0.055 × reps))

Widely used in scientific studies. Greater accuracy with more repetitions.

What is RPE?

RPE (Rating of Perceived Exertion) is the rate of perceived exertion. It's a 0-10 scale where 10 means total muscular failure and 0 means no effort. It directly relates to reps in reserve (RIR): RPE 9 = 1 rep in reserve, RPE 8 = 2 reps in reserve, etc. This metric allows adjusting the 1RM calculation based on how close you were to failure.

Beneficios

  • Calculate your 1RM without needing to perform an actual one-rep max, reducing injury risk
  • Uses the most accurate formulas: Epley (popular and general) and Mayhew (scientific)
  • Includes RPE adjustment for greater accuracy based on your perceived exertion
  • Perfect for bench press 1RM calculator, squat, deadlift, and any exercise
  • Shows working percentages (90%, 85%, 80%, etc.) to plan your training
  • 100% free and no registration required. Ideal for powerlifting and strength training

Frequently Asked Questions

How does the 1RM calculator work?
The 1RM calculator uses scientifically validated formulas (Epley and Mayhew) to estimate your one-rep max without needing to perform an actual maximum lift. Enter the weight lifted, reps completed, and RPE (rate of perceived exertion 0-10), and the calculator will estimate your 1RM adjusted for the effort the set required.
What is 1RM and why is it important?
1RM (One Rep Max) is the maximum weight you can lift for a single repetition in a given exercise. It's fundamental for programming strength training because it allows you to calculate specific working percentages (70%, 80%, 90% of 1RM) based on your goals of hypertrophy, strength, or power.
How do I use the bench press 1RM calculator?
To use the bench press 1RM calculator, select the Epley formula (recommended for bench press), enter the weight you lifted (e.g., 220 lbs), the reps you did (e.g., 5), and the RPE you felt (e.g., 8 if you could have done 2 more). The calculator will give you your estimated bench press 1RM and working percentages.
What's the difference between Epley and Mayhew?
The Epley formula is the most popular and accurate in 99% of cases, ideal for 1-10 repetitions. Mayhew is more commonly used in scientific studies and may be more accurate with higher rep ranges. Both are valid for 1RM calculation, but Epley is usually the most reliable for most exercises and rep ranges.
What is RPE in 1RM calculation?
RPE (Rating of Perceived Exertion) is the rate of perceived exertion on a 0-10 scale. RPE 10 means you reached total muscular failure, 9 means you could do 1 more rep, 8 means you could do 2 more, etc. This data is crucial for adjusting the 1RM calculation to make it more accurate based on how close you were to failure.
Is the 1RM calculator accurate for other exercises?
Yes, although it's often called a 'bench press 1RM calculator', the Epley and Mayhew formulas work for any exercise: squat, deadlift, overhead press, weighted pull-ups, etc. Accuracy is similar across all multi-joint exercises, though it may vary slightly depending on your experience with each movement.
When should I use the 1RM calculator?
Use the 1RM calculator when you need to know your max without doing an actual test (to avoid fatigue or injury), to program training cycles based on percentages, to track progress over time, or to set realistic goals for powerlifting or weightlifting competitions.