One Rep Max Calculator (1RM)
One rep max calculator: estimate your 1RM from the weight and reps of a set (Epley and Brzycki formulas), plus training weights at 85 % and 70 %.
1RM = w · (1 + r30)
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
1RM = weight × (1 + reps / 30) (Epley). Estimates are most reliable between 2 and 10 reps.
Use the percentages to plan strength (≈ 85 %) or hypertrophy (≈ 70 %) sets.
Formula
1RM = w · (1 + r30)
| Symbol | Quantity | Units |
|---|---|---|
| w | Weight lifted | kg, g, mg, µg, t, lb, oz, st, US ton, ct, Da |
| r | Repetitions | — |
| 1RM | One rep max | kg, g, mg, µg, t, lb, oz, st, US ton, ct, Da |
Constants used: Epley formula; best for 2–10 reps
Worked example
Given: w = 220.462 lb · r = 5
1RM = w (1 + r30)
Result: 1RM = 257.206 lb
One rep max for different values of Weight lifted
| w · Weight lifted | 1RM · One rep max |
|---|---|
| 176.4 lb | 205.76 lb |
| 198.4 lb | 231.49 lb |
| 220.5 lb | 257.21 lb |
| 242.5 lb | 282.93 lb |
| 264.6 lb | 308.65 lb |
| 286.6 lb | 334.37 lb |
Other values as in the worked example.
Frequently asked questions
225 lb for 5 reps?
Estimated 1RM ≈ 262.5 lb.
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