3 Rep Max (3RM) Calculator
Estimate the maximum load for 3 repetitions from a completed hard set. The main result is your predicted 3RM; the formula comparison also shows the underlying 1RM estimate.
Worked example: 100 kg for 3 reps
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 − 3) | 105.9 |
| Epley | 100 × (1 + 3 ÷ 30) | 110 |
| Lander | 10000 ÷ (101.3 − 2.67123 × 3) | 107.2 |
| O’Conner | 100 × (1 + 0.025 × 3) | 107.5 |
| Mean of four estimates | Calculated before rounding | 107.6 |
3RM to 1RM conversion table
Each row starts with a completed 3-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 3RM (kg) | Estimated 1RM (kg) | Predicted 3RM (kg) |
|---|---|---|
| 40 | 43.1 | 40.7 |
| 60 | 64.6 | 61 |
| 80 | 86.1 | 81.3 |
| 100 | 107.6 | 101.6 |
| 120 | 129.2 | 122 |
How to use the 3RM calculator
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 3 reps, but you can change it to match your set. Read the main 3RM result, compare the underlying 1RM formula estimates, then check the rep-max table.
A heavy triple is not a maximal single
A triple keeps the extrapolation relatively short, but technique and fatigue still matter. A set stopped well before failure does not reveal your true 3RM. Keep the same pause, depth and equipment when comparing sessions.
Turning the estimate into training
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.
Frequently asked questions
Is my 3RM the same as my 1RM?
No. A 3RM is a load you can complete for 3 repetitions. A 1RM is a single repetition. The calculator estimates the relationship; it does not test either maximum.
Why do the formulas disagree?
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.
Can I use kilograms or pounds?
Yes. The strength equations scale with the entered load. Keep every load in the same unit and read the output in that unit.
Should I enter a warm-up set?
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.
Methods and references
Reference tables use the same calculations and benchmark values as the interactive tool.