One-Rep Max Calculator
1 to 10 is most accurate
Estimated one-rep max
Enter the weight and reps of a recent set to estimate your one-rep max.
How to use the One-Rep Max Calculator
- Choose kg or lb, and the Epley or Brzycki formula. Epley is the default; both are shown in the result.
- Enter the weight you lifted and how many clean reps you completed. Sets of 1 to 10 reps give the most reliable estimate.
- Your estimated one-rep max appears straight away, with a table of training weights at common percentages.
Examples
- 100 kg for 5 reps gives an estimated 1RM of 116.7 kg with Epley, or 112.5 kg with Brzycki.
- 80 kg for 8 reps gives about 101.3 kg (Epley) or 99.3 kg (Brzycki).
- 225 lb for 3 reps gives about 247.5 lb (Epley) or 238.2 lb (Brzycki).
How the one-rep max is estimated
A one-rep max is the most weight you can lift once with good form. Testing it directly is tiring and carries more risk, so lifters often estimate it from a lighter set taken close to failure. The two most widely used formulas are:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
They agree closely at low reps and drift apart as reps rise. Brzycki gives the lower, more conservative figure up to 10 reps. A single rep is your 1RM by definition, so both return the weight itself.
Training percentages
Programmes often prescribe work as a percentage of your 1RM, for example 5 sets at 80%. The table multiplies your estimate by each percentage, and the reps column shows roughly how many reps that weight allows, using the Epley formula in reverse. To work out other percentages, use the Percentage Calculator.
An estimate, not a measurement
Every formula is an average across many lifters. Your true max depends on the lift, your training history, technique, fatigue and how close to failure the set really was. Estimates from more than 10 reps are much less reliable. Treat the number as a planning guide, and build up to heavy attempts gradually with proper technique and a spotter or safety bars.
Frequently asked questions
Which formula is most accurate?
Neither is best for everyone. Epley and Brzycki are both well established and give similar answers for sets of 1 to 6 reps. Use the same formula each time so your estimates are comparable as you get stronger.
How many reps should I use for the estimate?
A hard set of 3 to 6 reps, taken close to failure with good form, usually gives the best estimate. Above 10 reps, endurance plays a bigger part and the estimate becomes less reliable.
Does it work for any exercise?
The formulas were developed mainly for barbell lifts such as the squat, bench press and deadlift. They are a reasonable guide for other compound lifts, and less reliable for small isolation exercises and machines.
Can I switch between kg and lb?
Yes. Choose kg or lb before entering the weight. The result and the training table use the same unit, rounded to one decimal place.
Is my data stored?
No. The calculation runs in your browser and nothing is sent or saved. Reloading the page clears it.
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