One Rep Max Calculator
Estimate your one rep max (1RM) from any weight and rep count. This one rep max calculator uses the Epley and Brzycki formulas and builds a training percentage chart for every rep range.
Reviewed & updated for 2026 by Rakesh Choudhary, PhDMethodology & sources · How we calculate
Your training percentage chart
Working weights based on your estimated 1RM. Est. reps is what the two formulas, run backwards, predict you could manage at each percentage (the average of the two, rounded). The Goal column is a common coaching convention, not a standard.
| % of 1RM | Est. reps | Goal | Weight |
|---|---|---|---|
| Enter a lift to build your chart | |||
How 1RM is estimated
Your one rep max is the most weight you can lift for a single rep with good form. Testing it directly is risky, so coaches estimate it from a set you can already do. This calculator uses two published formulas, Epley (1985: 1RM = weight × (1 + reps ÷ 30)) and Brzycki (1993: 1RM = weight × 36 ÷ (37 − reps)), shows both and averages them. Neither is an official or clinical standard, so the result is an estimate.
The two formulas give the same figure at 10 reps. Below that Epley is slightly higher (3.7% apart at 5 reps); above it they split quickly (27% apart at 20 reps). For tracking progress, keep the rep count and exercise consistent and watch the estimate trend up over weeks.
For general fitness reference. Warm up, use a spotter, and progress gradually, don't load your estimated max without preparation.
Worked example: estimating from a real set
Suppose you bench press 185 lb for 5 clean reps. The two formulas estimate your one-rep max like this:
- Epley: weight × (1 + reps ÷ 30) = 185 × (1 + 5 ÷ 30) = 185 × 1.167 = 216 lb.
- Brzycki: weight × 36 ÷ (37 − reps) = 185 × 36 ÷ 32 = 185 × 1.125 = 208 lb.
Here the two are 3.7% apart. The calculator above takes their average, 212 lb, and applies it to the percentage chart so you can program your working sets. It is an estimate from published formulas, not a tested max.
FAQs
How do you calculate one rep max?
Start from a set you have already done: the load and how many clean reps you managed. An estimating equation then scales that load up to a single. Under Epley, 185 lb moved 5 times works out to about 216 lb; under Brzycki it comes to about 208 lb. This tool reports both and takes the midpoint, 212 lb.
What is the Epley vs Brzycki formula?
Epley (1985) multiplies the load by one plus the rep count over 30. Brzycki (1993) multiplies it by 36 and divides by 37 minus the reps. Epley reads a little higher for short sets, the pair match exactly at 10, and past that Brzycki climbs faster: at 20 reps it sits 27% above Epley.
How accurate is a 1RM estimate?
No official body publishes an accuracy figure for either equation, and neither is a clinical or official measure. The shorter the set, the less the answer leans on the equation, since a single rep is the max itself. A number projected from a long set is a rough guide, not a load to put on the bar untested. Test a true max carefully, with a spotter.
What percentage of 1RM should I train at?
No official standard sets these. The chart's goal column follows a common coaching convention: heavier loads and fewer reps for strength, moderate loads for muscle size, lighter loads and longer sets for endurance. A qualified coach can set percentages for your own program.
Should I actually attempt my estimated 1RM?
Not without preparation. Use the estimate to program training weights, then test a true 1RM only when well rested, warmed up, and with a spotter or safety bars. Beginners generally shouldn't max out, rep-based estimates are safer and nearly as useful for tracking progress.