One-rep max calculator

Enter a weight and the reps you managed close to failure, and this estimates your one-rep max (1RM) with the Epley and Brzycki formulas. For example, 100 kg for 5 reps works out to about 113 to 117 kg.

Weight lifted (kg)

Reps

Training percentages

Based on the average of the two estimates, rounded to the nearest 2.5 kg so you can load it with standard plates.

How to get a good estimate

Use a set where you couldn't have done more than one more rep with good form. A set you stopped well short of failure will underestimate your max. Re-check every few weeks off your best recent top set, rather than testing a single every time.

To see the trend, log your sets. Over months, a rising estimate on the same lift is a good sign your programme is working.

Questions

How do I calculate my one-rep max?

Take a set you did close to failure and put the weight and reps into a formula. Epley is weight × (1 + reps ÷ 30). Brzycki is weight × 36 ÷ (37 − reps). For 100 kg × 5, Epley gives 116.7 kg and Brzycki 112.5 kg.

Which 1RM formula is more accurate?

Neither is right for everyone. Between 1 and 12 reps the two land within 4% of each other, and they give the same answer at 10 reps. Both are estimates, so treat the result as a guide, not a tested max.

How many reps should I use?

Lower is better. An estimate from a hard set of 3 extrapolates far less than one from a set of 12. This calculator accepts 1 to 12 reps.

Should I test a true one-rep max?

You don't need to. A calculated max is enough to set training percentages. If you do test, warm up properly and use a spotter or safety bars.

Sources

1. Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance 1993;64(1):88–90. DOI
2. Epley B. Poundage chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985. Overview