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One-Rep Max (1RM) Calculator

Estimate your one-rep max from any submaximal set, compare six prediction formulas and get a full percent-of-1RM training table with a warm-up plan.

Pick a lift or load a preset set

Units

Weight lifted (kg) Total bar weight you lifted in the set. Reps completed Clean reps in one set, from 1 to 12. Fewer reps give a more accurate estimate.

Advanced: plate step and which formulas to average

Smallest plate pair / rounding step Training weights are rounded to a multiple of this step so they are loadable.

Formulas included in the average

Estimated one-rep max

0 kg

The heaviest weight you could lift once, averaged across the selected formulas.

Six formulas compared

Formula	Estimated 1RM	In plain words

Each formula models the rep-to-weight relationship differently. The averaged value smooths out their disagreement; unchecked formulas in the advanced panel are left out of the average.

Training weights by percent of 1RM

% of 1RM	Weight	Typical reps	Use it for

Weight is rounded to your selected plate step so every load is loadable on the bar. Typical reps come from reversing the Epley relationship.

Warm-up plan up to the working weight

Set	Weight	Reps	Note

The plan ramps from the empty bar to a working single near your estimated max. The final highlighted row is the working set itself.

For beginners: how to read this result

It is an estimate1RM is calculated from a sub-maximal set, not measured. Lower-rep sets predict it more reliably than high-rep sets.

Use percentages to programMost strength work sits between 70 and 90 percent of 1RM; lighter loads build volume, heavier ones build top-end strength.

It drifts over timeStrength, fatigue and technique change week to week. Re-test with a fresh hard set every few weeks.

These numbers are estimates from population formulas, not a guaranteed lift. Only attempt a true one-rep max with a competent spotter or safety rails, a proper warm-up and good technique. Stop if form breaks down.

To get a result, choose a lift, pick a quick preset set or type the weight you lifted and the reps you completed. The unit toggle switches between kilograms and pounds. The advanced section sets the plate-rounding step and lets you choose which formulas feed the average.

How the one-rep max is estimated

A one-rep max is the heaviest weight you could lift for a single repetition. Instead of testing it directly, this calculator predicts it from a submaximal set using six published equations and reports the average so no single formula dominates.

Epley: weight times one plus reps divided by 30.
Brzycki: weight times 36 divided by 37 minus reps.
Lombardi: weight times reps raised to the power 0.10.
McGlothin: 100 times weight divided by 101.3 minus 2.671 times reps.
Mayhew: 100 times weight divided by 52.2 plus 41.9 times e to the minus 0.055 times reps.
O’Conner: weight times one plus reps divided by 40.

When reps equal one, the lifted weight is itself the one-rep max. Estimates are most reliable from sets of one to five reps; high-rep sets widen the spread between formulas.

Percent-of-1RM training table

The percentage table converts the estimated max into loadable training weights from 50 to 100 percent, rounded to the chosen plate step, with a typical rep count for each percentage derived by reversing the Epley relationship. It answers the everyday question of how much weight to put on the bar for a given training goal.

Warm-up plan

The warm-up plan ramps from the empty bar through several ascending sets up to a working single near the estimated max, so the heaviest attempt is reached with a primed nervous system rather than a cold start.

What is not included

These formulas describe population averages, not your individual strength curve. They do not account for exercise type beyond the rounding step, fatigue, technique under maximal load, equipment, or day-to-day variation. A predicted max is a planning tool, not a guaranteed lift, and a real one-rep max attempt should only be made with a spotter or safety rails.