Back to Free Tools
8 Rep Max (8RM) Calculator
Estimate the maximum load for 8 repetitions from a completed hard set. The main result is your predicted 8RM; the formula comparison also shows the underlying 1RM estimate.
Estimate the maximum load for 8 repetitions from a completed hard set. The main result is your predicted 8RM; the formula comparison also shows the underlying 1RM estimate.
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 − 8) | 124.1 |
| Epley | 100 × (1 + 8 ÷ 30) | 126.7 |
| Lander | 10000 ÷ (101.3 − 2.67123 × 8) | 125.1 |
| O’Conner | 100 × (1 + 0.025 × 8) | 120 |
| Mean of four estimates | Calculated before rounding | 124 |
Each row starts with a completed 8-rep set. The 1RM column uses the mean of four equations; the final column converts that estimate back with inverse Brzycki. It may differ from the input.
| Completed 8RM (kg) | Estimated 1RM (kg) | Predicted 8RM (kg) |
|---|---|---|
| 40 | 49.6 | 40 |
| 60 | 74.4 | 59.9 |
| 80 | 99.2 | 79.9 |
| 100 | 124 | 99.9 |
| 120 | 148.8 | 119.9 |
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. The form starts at 8 reps, but you can change it to match your set. Read the main 8RM result, compare the underlying 1RM formula estimates, then check the rep-max table.
An eight-rep set depends more on fatigue tolerance than a single or triple. Different lifters can complete different numbers of repetitions at the same percentage of their maximum. Use the result as a range and confirm it across several sessions.
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.
No. A 8RM is a load you can complete for 8 repetitions. A 1RM is a single repetition. The calculator estimates the relationship; it does not test either maximum.
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.