One-Rep Max Calculator

How to use the one-rep max calculator

1. Choose pounds or kilograms at the top.
2. Enter the total weight you lifted, including the bar, and the number of clean reps you completed with good form.
3. Read the average estimate and the result from each equation, then use the percentage table to set loads for your training.

One-rep max formulas

Here w is the weight lifted and r the number of repetitions. Each equation was fitted to people lifting to failure, so they agree closely at low reps and drift apart as the reps go up: at 3 reps the highest estimate is 7.7% above the lowest, at 12 reps 12.3%. Epley and Brzycki give exactly the same answer at 10 reps. The calculator shows all five and their average, because no single equation is best for every lift or every lifter. A single (one rep) is treated as your 1RM itself.

Worked example

You bench 185 lb for 5 reps. Epley gives 185 × (1 + 5 ÷ 30) = 215.8 lb and Brzycki gives 185 × 36 ÷ 32 = 208.1 lb. Across all five equations the estimates run from 208.1 to 220.2 lb, with an average of 213.9 lb. In metric, 85 kg for 5 reps averages 98.3 kg. A working set at 80% would then be about 171 lb.

Multiplier by reps for each equation

Multiply the weight you lifted by the factor for your reps. These factors are computed with the same equations as the calculator.

Percentage of 1RM and reps

Solving the Brzycki equation for reps (r = 37 − 36 × percentage) gives the number of full reps you could expect at each load. The last column uses the 213.9 lb example.

Getting a reliable estimate

• Use 3 to 10 reps. The equations are least accurate above about 10 reps, where endurance starts to matter as much as strength.
• Count only clean reps. Stop the count when your form breaks down, not when the bar finally stops moving.
• Exercises differ. In a 1997 comparison of seven equations by LeSuer and colleagues, every equation underestimated the deadlift, by 9% to 14% on average. Treat estimates for machines and single-arm lifts as rough too.
• Re-test occasionally. As you get stronger, repeat a rep test every few weeks rather than chasing a true max.

Testing a real one-rep max puts a lot of strain on muscles, joints and blood pressure. Only attempt one with experience, a proper warm-up and a spotter or safety bars. This is not medical advice; talk to a doctor or registered dietitian before starting heavy training if you have a health condition. For conditioning work, the target heart rate calculator gives cardio zones.

Sources

• 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", J Strength Cond Res 1997;11(4):211–213.
• Brzycki M, "Strength testing: predicting a one-rep max from reps-to-fatigue", JOPERD 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", J Appl Sport Sci Res 1992;6(4):200–206.
• Epley B, Poundage Chart, Boyd Epley Workout, Lincoln, NE: Body Enterprises, 1985.
• Lombardi VP, Beginning Weight Training, Dubuque, IA: W.C. Brown, 1989; O'Conner B, Simmons J, O'Shea P, Weight Training Today, St Paul, MN: West Publishing, 1989.