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1 Rep Max (1RM) Calculator
Estimate your maximum single from a completed set, compare four equations, and use a reference table to plan lighter training loads.
Estimate your maximum single from a completed set, compare four equations, and use a reference table to plan lighter training loads.
These are estimates from the same equations used by the calculator. Enter pounds instead and the results stay in pounds. A completed single is returned unchanged.
| Formula | Calculation | Estimated 1RM (kg) |
|---|---|---|
| Brzycki | 100 × 36 ÷ (37 − 5) | 112.5 |
| Epley | 100 × (1 + 5 ÷ 30) | 116.7 |
| Lander | 10000 ÷ (101.3 − 2.67123 × 5) | 113.7 |
| O’Conner | 100 × (1 + 0.025 × 5) | 112.5 |
| Mean of four estimates | Calculated before rounding | 113.8 |
Inverse Brzycki estimates. These are approximate maximum loads for a rep count, not prescribed working weights or guaranteed repetitions.
| Target reps | Estimated load (kg) | % of 1RM |
|---|---|---|
| 1 | 100 | 100% |
| 3 | 94.4 | 94.4% |
| 5 | 88.9 | 88.9% |
| 8 | 80.6 | 80.6% |
| 10 | 75 | 75% |
| 12 | 69.4 | 69.4% |
Choose the exercise and enter the total load, including the bar, in one unit. Enter the repetitions actually completed with a consistent range of motion. Use a recent hard set rather than extrapolating from a warm-up. Read the main 1RM result, compare the underlying 1RM formula estimates, then check the rep-max table.
The equations infer maximal strength from repetitions; they do not measure it directly. Exercise choice, fatigue, technique and how close the set was to failure all affect the result. The mean is a convenient summary, not a validated confidence interval.
A predicted rep max assumes a hard set. Normal working sets often need a lighter load to leave repetitions in reserve. Start conservatively, use suitable safeties or a spotter, and adjust to the quality of your repetitions. Compare the same exercise over time rather than using the estimate as a promise.
1RM means the greatest load completed for one repetition with the chosen technique. A calculated 1RM is an estimate of that performance, not a tested lift.
Each equation models the relationship between load and repetitions differently. The spread is a reminder that repetition-based estimates are approximate. More decimal places do not mean more certainty.
Yes. The strength equations scale with the entered load. Keep every load in the same unit and read the output in that unit.
A set far from your limit usually understates your maximum. Use a recent, controlled hard set and note any repetitions left in reserve. There is no need to attempt an unsafe repetition for the calculator.
Reference tables use the same calculations and benchmark values as the interactive tool.