1RM calculator

Estimate your one-rep max from any set — no need to test a true max. Enter the weight and the reps you managed, and get your estimated 1RM plus the load for every training percentage.

Unit
Your estimated 1RM
—
Epley formula — the same one Lifter Log uses

By formula

Epley—
Brzycki—
Lombardi—

Training loads

% of 1RMWeight≈ Reps

What is a one-rep max?

Your one-rep max (1RM) is the heaviest weight you can lift for a single, full repetition with good form. Lifters use it to measure strength and to plan training: most programs prescribe weights as a percentage of your 1RM.

How the calculator works

Testing a true max is tiring and riskier without a spotter, so this calculator estimates it from a set you've already done. Each formula turns the weight and the reps you completed into a predicted single. Epley multiplies the weight by 1 + reps ÷ 30; Brzycki uses weight × 36 ÷ (37 − reps); Lombardi uses weight × reps^0.10. The formulas agree closely for sets of 1 to 10 reps and drift apart above that.

How to use your 1RM

Heavy strength work usually sits around 80–95% of your 1RM for low reps, muscle-building work around 65–85% for moderate reps, and lighter technique or endurance work below that. Use the chart above to turn any percentage into a weight on the bar, and re-estimate every few weeks as you get stronger.

Questions, answered

How accurate is a 1RM calculator?
For sets of about 2 to 10 reps taken close to failure, estimates are usually within a few percent of a tested max. Above 10 reps they become less reliable, because endurance starts to matter as much as strength.
Which 1RM formula is best?
None is perfect for everyone. Epley and Brzycki are the most widely used and give almost the same result between 2 and 10 reps. Lifter Log uses Epley to estimate your 1RM from the sets you log.
Should I test my real one-rep max?
You don't have to. An estimate from a hard set of 3 to 5 reps is enough to plan training. If you do test a true max, warm up thoroughly and use a spotter or safety bars.

More free tools

Plate calculator

Enter a target weight and see exactly which plates to load on each side of the bar.

Let Lifter Log track your 1RM for you

Lifter Log estimates your 1RM from the sets you log and charts it over time in Analytics — so you can see your strength climb without doing the math.

Download on theApp Store Get it onGoogle Play

30-day free trial · No card needed