1 Rep Calculator
1 rep calculator works out Estimated 1RM and Average across all seven equations from Weight lifted, Weight unit and Repetitions completed. The default figures on this page give estimated 1RM of 116.67; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
9 steps
- Epley: 116.67
- Brzycki: 112.5
- Lander: 113.71
- Lombardi: 117.46
- Mayhew et al.: 119.01
- O'Conner et al.: 112.5
- Wathan: 116.58
- Chosen estimate (epley) = 116.67 kg
- The set entered is 85.7% of that maximum.
Estimate from each equationtable
| formula | oneRepMax |
|---|---|
| Epley | 116.67 |
| Brzycki | 112.5 |
| Lander | 113.71 |
| Lombardi | 117.46 |
| Mayhew et al. | 119.01 |
| O'Conner et al. | 112.5 |
| Wathan | 116.58 |
Predicted weight for each rep counttable
| reps | weight | percentOfMax |
|---|---|---|
| 1 | 116.67 | 100 |
| 2 | 109.38 | 93.8 |
| 3 | 106.06 | 90.9 |
| 4 | 102.94 | 88.2 |
| 5 | 100 | 85.7 |
| 6 | 97.22 | 83.3 |
| 7 | 94.59 | 81.1 |
| 8 | 92.11 | 78.9 |
| 9 | 89.74 | 76.9 |
| 10 | 87.5 | 75 |
| 11 | 85.37 | 73.2 |
| 12 | 83.33 | 71.4 |
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
8 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the 1 rep calculator calculates
Estimates a one-repetition maximum from a set taken to or near failure using seven published rep-max equations, with the training percentages and rep-max table that follow from it.
How to use this 1 rep calculator
Enter Weight lifted, Weight unit, Repetitions completed and How hard was the set. Estimated 1RM updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Estimated 1RM, Average across all seven equations and Lowest of the seven equations.
The method follows Epley B - Poundage Chart, Boyd Epley Workout, University of Nebraska, 1985, Brzycki M - Strength testing: predicting a one-rep max from reps to fatigue, Lander J - Maximums based on reps, National Strength and Conditioning Association Journal 1985;6:60-61, Lombardi VP - Beginning Weight Training: The Safe and Effective Way, Wm. C. Brown, 1989 and Mayhew JL, Ball TE, Arnold MD, Bowen JC - Relative muscular endurance performance as a predictor of bench press strength.
Epley: 100 kg for 5 reps example
With Weight lifted: 100, Repetitions completed: 5, Equation: epley, How hard was the set: to-failure, the calculator returns Estimated 1RM: 116.67, The set you entered as a percentage of 1RM: 85.7, Repetitions used in the equation: 5. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Estimated 1RM, Average across all seven equations and Lowest of the seven equations. The inputs you can vary are Weight lifted, Weight unit, Repetitions completed, How hard was the set, RPE of the set and Equation.
Understanding Estimated 1RM, Average across all seven equations and Lowest of the seven equations
A predicted 1RM is an estimate from a submaximal set, not a tested maximum, and the error grows with the number of repetitions. Attempting a true maximal single without adequate warm-up, technique and spotting risks injury.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
What information do I need for the 1 rep calculator?
You need Weight lifted, Weight unit, Repetitions completed, How hard was the set, RPE of the set, Equation and Exercise. The page opens with default figures that give estimated 1RM of 116.67, so you can see the scale before entering your own.
What does this 1 rep calculator show?
It shows Estimated 1RM, Average across all seven equations, Lowest of the seven equations, Highest of the seven equations, Estimate from each equation, Predicted weight for each rep count, The set you entered as a percentage of 1RM and Repetitions used in the equation, with the working and any warnings for your entries.
Can I check how the 1 rep calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.