One Rep Max Calculator
Estimate your maximum lift for any exercise based on weight and reps.
Precision Fitness Calculators
Estimate your maximum lift for any exercise based on weight and reps.
lbs
How many reps did you complete with this weight?
Progressive Overload Tracker
Log your estimated 1RM each session to track strength gains over time. Data stays on your device.
No Squat sessions yet. Calculate your 1RM above and click "Log" to start tracking.
Scientific Reference
This calculator uses three established formulas and averages them for a more accurate estimate. These formulas are most accurate for rep ranges of 2–10.
The Formulas
- Epley (1985): 1RM = weight × (1 + reps ÷ 30)
- Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps)
- Lombardi (1989): 1RM = weight × reps0.10
Training Zones
- Strength (1–5 reps): 85–100% of 1RM
- Hypertrophy (6–12 reps): 65–85% of 1RM
- Endurance (13–20+ reps): 50–65% of 1RM
Estimate your max without maxing out
Your one rep max (1RM) is the heaviest weight you can lift once with proper form — and the anchor that every serious strength program percentages its sets from. Actually testing a true max is fatiguing and carries injury risk, which is why estimation formulas exist: lift a submaximal weight for as many clean reps as possible, and the math projects your max.
This calculator runs three validated formulas — Epley (weight × (1 + reps/30)), Brzycki (weight × 36/(37 − reps)) and Lombardi (weight × reps^0.10) — and averages them, which smooths each formula's individual bias. Accuracy is best in the 2–10 rep range; beyond 10 reps the relationship between reps and max weakens, so estimate from a heavier set instead.
Training with percentages and tracking overload
Once you know your 1RM, training zones become concrete: strength work lives at 85–100% for 1–5 reps, hypertrophy at 65–85% for 6–12 reps, and muscular endurance at 50–65% for 13–20 reps. A program that says "5 sets of 3 at 87.5%" now translates directly into kilograms on the bar.
The built-in Progressive Overload Tracker logs your estimated max for squat, bench and deadlift over time and charts the trend — because the single most reliable driver of strength gain is doing slightly more than last time, and you cannot manage what you never wrote down. Log a set every week or two per lift; a rising trend line across months matters far more than any single day's number.
Read the estimate with its limits in mind. Rep endurance varies between people and between lifts: a lifter with high muscular endurance will grind out 10 reps at a weight the formulas expect to allow 8, which inflates the projection. Deadlifts in particular tend to over-estimate because grip and lower-back fatigue cap high-rep sets before the prime movers give out. This matters less than it sounds, though, because the number you care about is the trend. If you always estimate from the same lift at the same rep range, whatever bias exists stays constant and cancels out, leaving a clean read on whether you are actually getting stronger.
Frequently Asked Questions
How accurate are 1RM formulas?
Within about 2–5% for sets of 2–10 reps, with accuracy dropping as reps climb. Averaging multiple formulas, as this calculator does, reduces the bias any single equation carries for your rep style.
Should beginners test a true one rep max?
No. In the first year of training, estimated maxes from 5-rep sets provide everything a program needs without the injury risk of grinding a maximal single. Save true max attempts until technique is stable under heavy load.
How often should my 1RM go up?
Beginners can add weight almost weekly; intermediates should expect monthly progress; advanced lifters fight for kilograms per year. If your estimated max has been flat for 6+ weeks, change the stimulus — volume, frequency or exercise variation.
What percentage of 1RM builds muscle best?
Hypertrophy responds well to the 65–85% range for 6–12 reps, but research shows lighter loads build comparable muscle when sets approach failure. Percentages matter most for strength work, where heavy specificity is non-negotiable.