One Rep Max Calculator

What is a one-rep max?

A one-rep maximum, or 1RM, is the estimated heaviest load a person can lift for one complete repetition of a specific exercise with sound technique. It is exercise-specific: a bench press 1RM is not interchangeable with a squat or deadlift 1RM.

How this calculator works

Enter the weight you lifted and the number of completed repetitions. DigiSadhan runs seven commonly used prediction equations: Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner and Wathen. Research literature contains comparisons of these equations, and published versions include the equations shown here. citeturn0search0

Why show seven formulas?

Different equations can produce different answers because they model the relationship between repetitions and maximal strength differently. The difference becomes more noticeable as repetition count increases. Showing the full range is more honest than presenting one number as exact. citeturn0search2turn0search4

Epley

1RM = weight × (1 + reps / 30). It is one of the most widely used general-purpose equations.

Brzycki

1RM = weight × 36 / (37 − reps). The equation becomes mathematically unsuitable as repetitions approach 37, which is why this tool limits practical inputs.

Lander

1RM = 100 × weight / (101.3 − 2.67123 × reps).

Lombardi

1RM = weight × reps0.10.

Mayhew

1RM = 100 × weight / (52.2 + 41.9 × e−0.055 × reps). This equation is associated with bench-press prediction research, so it should not be treated as universally superior for every lift.

O'Conner

1RM = weight × (1 + 0.025 × reps).

Wathen

1RM = 100 × weight / (48.8 + 53.8 × e−0.075 × reps).

Median vs average

The default headline uses the median of the seven estimates because it reduces the influence of an unusually high or low equation. The average is also available. Neither should be interpreted as a laboratory measurement.

Rep range and reliability

Prediction equations generally become less dependable as reps rise far beyond the ranges in which they were developed or validated. Recent literature has compared several of these equations in specific populations and exercises, reinforcing that equation performance depends on the lift and population. citeturn0search0

Training percentage table

The calculator converts the headline estimate into loads from 50% to 100%. These percentages are planning references, not prescriptions. Your actual training load should reflect technique, fatigue, exercise selection, recovery and your program.

Relative strength

If bodyweight is entered, the calculator reports estimated 1RM divided by bodyweight. This is useful for comparing your own progress over time, but it should not be treated as a universal ranking because standards differ by exercise, sex, training history and population.

True 1RM testing

A predicted 1RM is useful precisely because you do not have to test a maximal single frequently. If you do attempt a true max, use appropriate warm-up, equipment, technique, safety supports and qualified supervision. Never let the calculator encourage a risky attempt.

How to improve the estimate

Use a recent set performed with consistent technique and a clear repetition count. Avoid estimating from a set performed while unusually fatigued or with a large change in range of motion. For ongoing training, repeat the same calculation periodically and compare trends rather than obsessing over a single decimal.

Why the result can differ from your actual max

Individual strength-endurance profiles vary. A lifter who is good at high repetitions may get a different prediction than a lifter who is highly specialized in singles. Exercise mechanics, fatigue, technique, pause rules, equipment, tempo and motivation also matter.

DigiSadhan approach

The page is designed to be clear on mobile, transparent about the mathematics and conservative about claims. Animated graphics help users see the result and formula spread, but the animations do not add accuracy.

Disclaimer

This is an educational fitness calculator, not a medical or performance-lab assessment. Estimated 1RM values can be wrong. Do not use them as a reason to exceed safe loading. Stop exercise for pain, dizziness or other concerning symptoms and seek appropriate professional advice.