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 · How we calculate
Your training percentage chart
Working weights based on your estimated 1RM, the percentage you use depends on whether you're training for strength, size, or endurance:
| % 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. The two most common formulas are Epley (1RM = weight × (1 + reps ÷ 30)) and Brzycki (1RM = weight × 36 ÷ (37 − reps)). This calculator shows both and averages them.
Estimates are most accurate in the 1–5 rep range. Above roughly 10 reps, fatigue and technique vary so much that the number becomes a rough guide. 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.
FAQs
How do you calculate one rep max?
Enter a weight you lifted and the number of clean reps, then a formula estimates the max you could lift once. The popular Epley formula is 1RM = weight × (1 + reps ÷ 30). For example, 185 lb for 5 reps ≈ 185 × (1 + 5/30) = 216 lb. The calculator averages several formulas for a more reliable estimate.
What is the Epley vs Brzycki formula?
Both estimate 1RM from submaximal lifts. Epley: 1RM = w × (1 + reps/30). Brzycki: 1RM = w × 36 ÷ (37 − reps). They agree closely at low reps and diverge above about 10 reps, where all 1RM estimates become less accurate. This tool shows both and an average.
How accurate is a 1RM estimate?
Most accurate at 1–5 reps, where estimates are usually within a few percent of a true max. Accuracy drops as reps rise, because endurance and technique vary more, so a 1RM estimated from a 15-rep set is a rough guide, not a number to load on the bar blindly. Test true maxes carefully with a spotter.
What percentage of 1RM should I train at?
It depends on the goal. Strength: 85–100% for 1–5 reps. Hypertrophy (muscle size): 67–85% for 6–12 reps. Endurance: under 67% for 12+ reps. The percentage chart on this page converts your estimated 1RM into working weights for each rep range.
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.