One rep max calculator

You do not need to test a true max. Put in a hard set you did recently and get a fair estimate of your one rep max, plus the weights for other rep ranges.

Your details

Weights in
Weight lifted
Clean reps

Estimated one rep max from 80 kg × 5

93.3 kg

Epley formula

  • Brzycki formula90 kg
  • Average of the two91.7 kg
  • Likely 3 rep max85 kg
  • Likely 5 rep max80 kg
  • Likely 8 rep max72.5 kg
  • Likely 10 rep max70 kg

This is an estimate from a hard set, so you never need to test a true max to train well. Sets of 3 to 6 reps give the closest estimates.

Sharp pain, a pop, or pain that lingers after a session is a reason to stop and see a GP or physio. Chest pain or feeling faint while lifting: stop, and call 999 if it does not pass.

The working

80 kg for 5 reps

Epley: 80 × (1 + 5 ÷ 30) = 93.3 kg. Brzycki: 80 × 36 ÷ (37 − 5) = 90 kg. Your likely 3 rep max is about 85 kg, your 8 rep max about 72.5 kg and your 10 rep max about 70 kg.

Which formula?

Close enough is fine

Both formulas came from lifters doing sets to failure. They agree closely at low reps and drift apart above 10, which is why this page stops at 12. Studies comparing them find errors of a few kilos either way, more for lifts you rarely train.

Using it

What to do with the number

  • Plan your sets from it with percentages
  • Recheck every 6 to 8 weeks from a hard set
  • Use a set you did with good form, not a grind
  • Squat and deadlift estimates run a little higher than bench

Read with care

What this cannot tell you

  • A true maxOnly a tested single is your real max, and testing carries more risk.
  • FormA set with poor depth or a bounce gives a flattering number.
  • MachinesMachine weights vary by brand, so estimates do not carry across.

Questions

Common questions

How accurate is a one rep max calculator?

Usually within about 5% from a set of 3 to 6 reps; less accurate above 10 reps.

Should I test my one rep max?

You do not need to. An estimate from a hard set works for planning and is safer.

What is the Epley formula?

One rep max = weight × (1 + reps ÷ 30).

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

Before you push on

New to exercise, or got a heart, lung or joint condition? Have a word with your GP or practice nurse first. Stop and get help if you feel chest pain, faintness or unusual breathlessness, and call 999 if it is severe.

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