One rep max calculator

How to calculate your one rep max

1. Select your exercise: bench press, squat, or deadlift.
2. Enter the weight you lifted and the number of reps performed (1–12).
3. Your estimated 1RM appears alongside both Epley and Brzycki formula results.
4. Use the training percentage table to set your working weights for each intensity zone.

Common uses

• Setting training percentages for a powerlifting or strength programme
• Tracking strength progress without attempting an actual maximum effort, alongside a body fat calculator for a full picture of progress
• Comparing relative strength between lifters of different sizes by dividing the estimate by bodyweight, or by estimated lean mass

Technical specification

• Algorithm or formula: Epley formula 1RM = w * (1 + r/30) (Boyd Epley, 1985) and Brzycki formula 1RM = w * 36/(37-r) (Matt Brzycki, 1993), where w is the weight lifted and r is the rep count. The displayed estimate is the average of the two.
• Browser API or library: Pure JavaScript arithmetic; no external library.
• Input limits: Weight 1–2,000 (lb or kg). Reps 1–12 (formula accuracy degrades above this range).
• Output: Estimated 1RM from each formula, plus a training percentage table from 60% to 100% in 5% steps showing the working weight at each intensity.
• Known limitations: Formula-based estimate, not a substitute for an actual tested 1RM. Accuracy decreases as rep count increases (most accurate in the 3–5 rep range).

Frequently asked questions

How do you calculate a one rep max?

Multiply the weight lifted by (1 + reps ÷ 30) for Epley, or by 36 ÷ (37 − reps) for Brzycki, then average the two. A set of 100 kg for 5 reps gives about 117 kg (Epley) and 113 kg (Brzycki), so the calculator shows 115 kg. Results are estimates for informational purposes only.

What is a one rep max (1RM)?

Your one rep max is the maximum weight you can lift for a single repetition with proper form. It is the standard measure of maximal strength and is used to calculate training loads as percentages.

Do I need an account to use this calculator?

The calculator works without an account. Enter the weight and reps, and your 1RM and training table appear immediately. All calculations run in your browser. Our servers are not involved at any point.

Which rep range gives the most accurate 1RM estimate?

Sets of 3–5 reps give the most accurate estimates. As rep counts increase above 8–10, endurance factors influence performance and the formulas become less reliable.