How the estimate works

Each formula turns a set of submaximal reps into an estimated single. One rep returns the weight itself. For more reps, this calculator averages:

• Brzycki (1993): weight / (1.0278 - 0.0278 x reps), which is weight x 36 / (37 - reps). Brzycki wrote that it holds when reps to fatigue stay under about 10.
• Epley: weight x (1 + 0.0333 x reps). The same equation appears as the Welday equation in the 2024 study below.
• Lombardi: weight x reps to the power of 0.1. The 2024 study found it the most accurate for men in the bench press and squat.

Sources: Brzycki M. Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue. JOPERD, 1993; Ribeiro A. and colleagues. Accuracy of 1RM Prediction Equations Before and After Resistance Training in Three Different Lifts. International Journal of Strength and Conditioning, 2024.

The percentage chart

Your result includes a chart from 100 down to 50 percent of your estimated max. The reps column comes from the Brzycki relationship and stops at 75 percent (about 10 reps), where the formula stops being reliable.

Relative strength

Divide your one rep max by your bodyweight and you get relative strength, the fairest way to compare lifters of different sizes. A 1.5 x bodyweight deadlift means the same thing at 150 lb as it does at 250 lb.

Frequently Asked Questions

What is a one rep max?

Your one rep max (1RM) is the most weight you can lift for one full repetition with good form. Most strength programs set training loads as a percentage of it, which is why the chart below matters as much as the number.

Which one rep max formula is most accurate?

No single formula wins for every lift and every lifter, so this calculator averages three common ones: Brzycki, Epley and Lombardi. In a 2024 study of 119 young adults tested before and after 16 weeks of training, the Lombardi equation was the most accurate for men in the bench press and squat, and the Brzycki equation was among the closest for women in both lifts (Ribeiro and colleagues, International Journal of Strength and Conditioning).

How many reps should I use to estimate my max?

A hard set of 3 to 10 reps works best. Brzycki wrote that his formula holds when reps to fatigue stay under about 10 and gets less accurate above that. This calculator accepts up to 12 reps and warns you past 10.

What is relative strength?

Relative strength is your lift divided by your bodyweight. A 300 lb deadlift at 200 lb bodyweight is 1.5 times bodyweight. It lets lifters of different sizes compare numbers. This calculator does not rank you against anyone. See where your lift actually ranks: Radar, free on 11/11.

Is it safe to test a true one rep max?

Brzycki pointed out that heavy 1RM attempts can place "an inordinate and unreasonable amount of stress" on the body. Estimating from a submaximal set avoids most of that. If you do test a true max, warm up thoroughly and use a spotter or safety bars.

How do I use the percentage chart?

Each row is a percentage of your estimated 1RM and the load it works out to, plus the reps you can expect at that load from the Brzycki relationship (about 10 reps at 75 percent). When a program calls for sets at 80 percent, use the 80 percent row.