About the One Rep Max Calculator
This one rep max calculator estimates the heaviest weight you could lift for a single repetition, based on a set you have already done. Enter the weight and the number of clean reps you completed and it returns your estimated 1RM using seven published formulas — Epley, Brzycki, Lombardi, Mayhew, O’Conner, Wathan and Lander — or their average.
Testing a true max is tiring and carries more injury risk, so most lifters and coaches estimate it from a submaximal set instead. The result feeds straight into percentage-based programs such as 5/3/1 or any plan that prescribes loads like “4 sets of 6 at 80%”. The load chart below the result lists common percentages with the reps you should be able to perform at each.
Estimates are most accurate for sets of 2–10 reps taken close to failure. Above 10–12 reps the formulas spread apart and muscular endurance starts to matter more than strength, so use a heavier set when you can. Units do not matter: enter pounds or kilograms and the answer comes back in the same unit.
With the default inputs, the estimated one rep max is 262.5. Change any value above to recalculate instantly.
How to use the one rep max calculator
- 1Warm up and perform a set close to failure with good form.
- 2Enter the weight you lifted and the reps you completed.
- 3Pick a formula, or use the average of all seven for a balanced estimate.
- 4Read your estimated 1RM and compare the spread across formulas.
- 5Use the load chart to set working weights for your program.
Formula and method
Each formula was fitted to data from lifters who performed both a rep-max set and a true 1RM test. Epley and Brzycki are the most widely used and agree closely at around 10 reps; Brzycki is slightly more conservative below that. Mayhew and Wathan use exponential curves and tend to give higher numbers for low-rep sets.
If you did exactly one rep, every formula returns the weight itself. The percentage table multiplies your chosen estimate by standard loads and lists the approximate repetitions most trained lifters can complete at each percentage, based on the widely used NSCA %1RM chart. Individual results vary with training history and muscle-fibre type.
- w
- Weight lifted in the set (any unit)
- r
- Repetitions completed
- 1RM
- Estimated one-repetition maximum
Worked examples
Bench press: 225 lb for 5 reps (Epley)
Epley gives 225 × (1 + 5 ÷ 30) = 262.5 lb. Brzycki is a little lower at 225 × 36 ÷ 32 = 253.1 lb, and the average of all seven formulas is about 259.9 lb.
Squat: 100 kg for 8 reps (Brzycki)
Brzycki estimates 100 × 36 ÷ (37 − 8) = 124.1 kg. Epley gives 126.7 kg and O’Conner 120 kg, so a realistic max is in the low-to-mid 120s.
Deadlift: 315 lb for 3 reps (average)
Averaging the seven formulas gives about 344 lb. Estimates range from Brzycki’s 333.5 lb up to Mayhew’s 359.1 lb, which is why low-rep sets still leave some uncertainty.
Frequently asked questions
How accurate is a one rep max calculator?+
For sets of 2–10 reps taken near failure, most formulas land within about 5% of a tested max. Accuracy drops with higher reps, poor form, or sets that stop well short of failure.
Which 1RM formula is best?+
No formula is best for everyone. Epley and Brzycki are the most validated and popular; averaging several formulas reduces the chance that one outlier skews your training loads.
Should I test my one rep max?+
Testing a true max is useful before a meet or at the end of a training block, but it needs a warm-up, spotters or safety bars, and good technique. Estimating from a 3–5 rep set is safer for most people.
What percentage of 1RM should I train at?+
Strength work usually uses 80–90% of 1RM for 2–6 reps, hypertrophy 65–80% for 6–12 reps, and muscular endurance below 65% for 15 or more reps.
Does the calculator work for any lift?+
Yes. The formulas apply to compound barbell lifts such as bench, squat, deadlift and overhead press. They are less reliable for isolation exercises and machines, where fatigue builds differently.