One Rep Max (1RM) Calculator

Enter the weight you lifted and how many reps you completed. The tool runs two practitioner formulas and shows their average:

• Epley: 1RM = weight × (1 + reps ÷ 30)
• Brzycki: 1RM = weight × 36 ÷ (37 − reps)

With the defaults, 100 for 5 reps, Epley gives 116.7 and Brzycki gives 112.5, so the tool shows 114.6. The box is labelled kg or lb because the formulas don't care about units: the answer comes back in whatever unit you typed. The number is an estimate of what one maximal rep might be, not a test result, and it says nothing about what is safe for you to attempt.

Under the estimate, the tool lists 100% down to 70% of it in 5% steps. For the default set:

If a programme asks for sets at 75% of your max, this saves you the multiplication. Round to the plates you actually have: 85.9 kg becomes 85 or 87.5 on most bars.

The two formulas give identical answers at exactly 10 reps: 80 for 10 is 106.7 either way. Away from 10 they separate, and the gap grows quickly with high reps:

• 225 for 3: Epley 247.5, Brzycki 238.2, shown as 242.9.
• 60 for 15: Epley 90.0, Brzycki 98.2, shown as 94.1.
• 100 for 20: Epley 166.7, Brzycki 211.8, shown as 189.2.

Both are generally treated as most reliable at about 10 reps or fewer, so a heavier set of 3 to 8 makes a better input than a long, light one. The reps box is set up for 1 to 20; beyond that, Brzycki's divisor shrinks towards zero and the estimate stops meaning anything.

Enter 100 for 1 rep and the tool shows 101.7, not 100. Brzycki returns exactly 100 at one rep, but Epley still adds a thirtieth, and the average splits the difference. If you have a true single, that lift is your 1RM and the calculator adds nothing.