Free & private

One Rep Max Calculator

Estimate your one-rep max (1RM) from the weight you lifted and the reps you performed, with a rep-max percentage table for programming your training.

Your lift

Enter a recent, honest set to failure for the best estimate.

kg
reps
🏋Your result will appear hereAdd the weight lifted and reps performed, then select estimate.
Estimated one-rep max (Epley)
0kg
0Brzycki estimate
0Average of both
% of 1RMApprox. weightTypical reps

Estimates are most reliable for sets of about 10 reps or fewer. Actual performance can vary with technique, fatigue and experience.

How to use the one-rep max calculator

This free calculator works in kilograms or pounds. Enter the weight you lifted and the number of clean reps you completed with good form, then select estimate. Everything runs locally in your browser, so nothing is uploaded or stored by this tool.

1. Choose your unit

Switch between kilograms and pounds to match your gym.

2. Enter weight & reps

Use a recent set taken close to muscular failure for accuracy.

3. Review your 1RM

See your estimated max plus a full rep-max percentage table.

Understanding your 1RM estimate

A one-rep max (1RM) is the most weight you could lift for a single repetition. Testing a true 1RM directly can be fatiguing and risky, so lifters commonly estimate it from a lighter set taken close to failure using a proven formula.

Epley formula

1RM = weight × (1 + reps ÷ 30). This is the primary estimate shown above.

Brzycki formula

1RM = weight × 36 ÷ (37 − reps), valid for reps under 37, shown for comparison.

Using the % table

Use the percentage table to plan working weights for strength, hypertrophy or power-focused training blocks.

How is one-rep max estimated?

This calculator uses the Epley formula, 1RM = weight × (1 + reps ÷ 30), as the primary estimate, and also shows the Brzycki formula for comparison.

Why do Epley and Brzycki give different results?

Each formula models the relationship between reps and load slightly differently. Both are estimates and tend to be more accurate for sets of around 10 reps or fewer.

What is a rep-max percentage table used for?

It shows approximate training loads at different percentages of your one-rep max, which is useful for programming strength, hypertrophy or power-focused sets.

Is this one-rep max calculator accurate?

It provides a useful estimate, but your actual max can differ due to technique, fatigue and experience. It is not a substitute for a supervised max test.

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