One Rep Max Calculator

Estimate the most you could lift for a single rep from a set you've already done, and get training weights for any percentage of your max.

Most accurate under 10 reps; up to 12.

What is a one-rep max?

Your one-rep max (1RM) is the heaviest weight you can lift for a single complete rep with good form. Strength programs use it as a reference point: instead of naming a weight, they prescribe a percentage of your max, such as 5 sets of 5 at 80%. Testing a true max is tiring and carries more risk, so most lifters estimate it from a harder set of several reps instead.

How the estimate is calculated

The calculator runs three widely used formulas on the weight and reps you enter, then averages them. w is the weight lifted and r the number of reps:

Epley: 1RM = w × (1 + r ÷ 30)

Brzycki: 1RM = w × 36 ÷ (37 − r)

Lombardi: 1RM = w × r^0.10

For example, 100 kg for 5 reps gives about 116.5 kg (Epley), 112.5 kg (Brzycki), and 117.5 kg (Lombardi), so the estimated max is about 115.5 kg. If you enter a single rep, that weight is your max and no formula is applied.

How to use this calculator

Pick kg or lb, enter the weight of a recent hard set and the number of reps you completed with good form, then press Calculate 1RM. The best set to use is one taken close to failure in the 3–8 rep range. You'll get the estimated max, each formula's result, and a table of training weights from 100% down to 65% of your max with the reps most people can manage at each.

Using percentages in training

Heavy work for strength usually sits at 80–90% of 1RM for 2–6 reps. For muscle growth the load matters less: studies find that sets from about 30% of 1RM upward build similar muscle when they're taken close to failure, though heavier sets build more strength. Re-estimate your max every few weeks as you get stronger so your training weights keep pace — that steady increase in load is progressive overload.

Lifts to estimate

The estimate works for any lift; these barbell lifts have 3D form guides:

Limitations

Rep-max formulas are averages and get less accurate as reps rise, especially past 10. In testing they predict the bench press and squat fairly well but tend to underestimate the deadlift, and people with a lot of muscular endurance can do more reps at a given percentage than the chart suggests. Treat the result as a working estimate, not a number to chase on a max attempt. If you do test a max, warm up thoroughly and use a spotter or safety arms — see the Disclaimer.

Read the science

References

The formulas and figures on this page come from these sources. Our Editorial Policy explains how they're chosen and checked.

  • Epley formula: Epley, B. (1985). Poundage chart. In Boyd Epley workout. Body Enterprises.
  • Brzycki formula: Brzycki, M. (1993). Strength testing—Predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88–90. doi:10.1080/07303084.1993.10606684
  • Lombardi formula: Lombardi, V. P. (1989). Beginning weight training: The safe and effective way. W. C. Brown.
  • Percent of 1RM and reps chart: Haff, G. G., & Triplett, N. T. (Eds.). (2016). Essentials of strength training and conditioning (4th ed.). Human Kinetics.
  • Accuracy for the bench press, squat, and deadlift: LeSuer, D. A., McCormick, J. H., Mayhew, J. L., Wasserstein, R. L., & Arnold, M. D. (1997). The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research, 11(4), 211–213. doi:10.1519/00124278-199711000-00001
  • Light and heavy loads for muscle growth: Schoenfeld, B. J., Grgic, J., Ogborn, D., & Krieger, J. W. (2017). Strength and hypertrophy adaptations between low- vs. high-load resistance training: A systematic review and meta-analysis. Journal of Strength and Conditioning Research, 31(12), 3508–3523. doi:10.1519/JSC.0000000000002200