1RM calculator

Training programs often prescribe a percentage of your 1RM, such as 5 x 5 at 80%. This table works that out for your 1RM, rounded to what you can load on the bar. The reps come from the table in the NSCA textbook (Haff and Triplett, 2016). In studies, many people manage more reps than the table says at the lighter weights.

No formula knows your 1RM exactly. But some formulas make a good estimate from a heavy set of several reps. The two best known are Epley and Brzycki:

Epley: 1RM = weight × (1 + reps / 30)

Brzycki: 1RM = weight × 36 / (37 − reps)

Example: 80 kg for 8 reps. Epley gives 80 × (1 + 8/30) = 101.3 kg, Brzycki gives 80 × 36 / 29 = 99.3 kg. This calculator takes the average: 100.3 kg. Up to about 10 reps the two formulas stay close; above that they drift apart and every estimate gets less certain.

A real 1RM test is hard on your muscles and joints, needs a proper warm-up and a spotter, and costs you a few days of recovery. For most people that is not worth it: an estimate from a set of 3 to 8 reps is usually close enough to base your training on.

Tip: use a set that was hard but with good technique, and calculate each exercise separately. Your bench press 1RM says nothing about your squat or deadlift.