How it works
Your one-rep max (1RM) is the most you can lift once with good form. Testing it directly is tiring and carries more risk, so most lifters estimate it from a heavier set taken close to failure. If you can squat 100 kg for 5 reps, you can lift more than 100 kg once, and the equations estimate how much more.
Researchers and coaches have published several of these equations. For sets of up to 10 reps they land within about 8 percent of each other. Above 10 reps they spread out quickly. This calculator shows all seven side by side and uses their average by default, which avoids leaning on any one of them.
The same equation also works in reverse. That is how the rep max table estimates what you could lift for 3, 8 or 10 reps.
The formula
w = weight lifted, r = reps completed
Epley 1RM = w × (1 + r ÷ 30)
Brzycki 1RM = w × 36 ÷ (37 − r)
Lander 1RM = 100 × w ÷ (101.3 − 2.67123 × r)
Lombardi 1RM = w × r^0.10
Mayhew 1RM = 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r))
O'Conner 1RM = w × (1 + 0.025 × r)
Wathen 1RM = 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r))
With 1 rep, the one-rep max is simply the weight lifted.Worked example
You bench 100 kg for 5 reps.
- Epley: 100 × (1 + 5 ÷ 30) = 116.7 kg.
- Brzycki: 100 × 36 ÷ (37 − 5) = 112.5 kg.
- The other five give 113.7 kg (Lander), 117.5 kg (Lombardi), 119.0 kg (Mayhew), 112.5 kg (O'Conner) and 116.6 kg (Wathen).
- The average of all seven is 115.5 kg, so a working set at 80% would be about 92.5 kg.
Questions
Which equation is the most accurate?
None is best for everyone. Accuracy depends on the lift, the rep count and the lifter. The average of several equations is a sensible default, and the spread between them shows how uncertain the estimate is.
How many reps give the best estimate?
Fewer is better. A set of 3 to 6 reps taken close to failure gives a tighter estimate than a set of 12, where the equations spread out. Use a set where you had at most a rep or two left.
Should I test a true one-rep max?
Only if you have lifting experience, a spotter or safety bars, and a reason to, such as a competition. For planning training, an estimate from a heavy set is usually enough and much less fatiguing.
Does it work for every exercise?
The equations were built from big barbell lifts such as the bench press and squat. They are less reliable for machines, isolation exercises and the deadlift, where reps to failure vary more between people.
How do I use the percentage table?
Training programs often prescribe sets as a percentage of your one-rep max, such as 5 sets of 5 at 75%. The table shows those weights, rounded to plates you can load.
Sources
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation and Dance. 1993;64(1):88-90.
- Mayhew JL, Ball TE, Arnold MD, Bowen JC. Relative muscular endurance performance as a predictor of bench press strength in college men and women. Journal of Applied Sport Science Research. 1992;6(4):200-206.
- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research. 1997;11(4):211-213.
- Epley B. Poundage Chart. Boyd Epley Workout; 1985. Lander J. Maximums based on reps. NSCA Journal. 1985. Lombardi VP. Beginning Weight Training. 1989. O’Conner B, Simmons J, O’Shea P. Weight Training Today. 1989. Wathen D. Load assignment. In: Essentials of Strength Training and Conditioning. 1994.