One Rep Max Calculator (1RM)
Estimate your one-rep max from a sub-max set. Compares Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan formulas.
HEALTHEstimate your one-rep max (1RM) for bench press, squat, deadlift, or any compound lift from a sub-max set. Compares seven validated formulas (Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, Wathan) and outputs a training-percentage table.
Each formula reaches 1RM from weight × reps differently. Epley: 1RM = w × (1 + r/30). Brzycki: 1RM = w × 36/(37-r). They converge for 1-5 reps and diverge above 10. Use a true near-failure set (1 rep in reserve) for accuracy. The percentage table maps 1RM percentages to typical rep ranges: 90%+ for singles, 80% for 6-8 reps, 70% for 10-12 reps, 60% for 15+.
One Rep Max Calculator (1RM)
Estimate your one-rep max (1RM) for bench press, squat, deadlift, or any lift from a sub-max set. Compare Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan formulas.
By Formula
| Formula | Estimate |
|---|---|
| Epley | 263 lbs |
| Brzycki | 253 lbs |
| Lander | 256 lbs |
| Lombardi | 264 lbs |
| Mayhew | 268 lbs |
| O'Conner | 253 lbs |
| Wathan | 262 lbs |
Training Percentages (% of 1RM)
| Percent | Reps | RIR | lbs |
|---|---|---|---|
| 100% | 1 | 0 | 260 |
| 95% | 2 | 0-1 | 247 |
| 93% | 3 | 0-1 | 242 |
| 90% | 4 | 0-1 | 234 |
| 87% | 5 | 1 | 226 |
| 85% | 6 | 1-2 | 221 |
| 83% | 7 | 1-2 | 216 |
| 80% | 8 | 2 | 208 |
| 77% | 9 | 2 | 200 |
| 75% | 10 | 2-3 | 195 |
| 70% | 12 | 3 | 182 |
| 65% | 15 | 3-4 | 169 |
| 60% | 20 | 4+ | 156 |
How 1RM Calculation Works
Your one-rep max (1RM) is the heaviest weight you can lift for a single rep with full range of motion. Testing it directly is risky and tiring, so coaches estimate 1RM from a sub-max set using validated formulas. The Epley formula is the most common: 1RM = weight × (1 + reps/30). Brzycki: 1RM = weight × 36/(37-reps). These give similar results for 1-5 reps but diverge as reps climb.
Use a true near-failure set for accuracy. If you did 225 lbs × 5 reps with 1 rep in reserve (RIR 1), your estimated 1RM is around 257 lbs (Epley: 225 × 1.167 = 263; Brzycki: 225 × 1.125 = 253). Above 10 reps, the formulas overestimate because muscular endurance and 1RM strength are governed by different physiology.
Training percentages of 1RM drive program design: 90%+ for max strength singles, 80-90% for heavy 3-5s, 70-80% for hypertrophy 6-10s, 60-70% for moderate-volume 10-15s. Stick to compound lifts (bench, squat, deadlift, OHP) for 1RM testing - isolation exercises like curls do not have well-validated 1RM formulas.
Estimates only. Actual 1RM varies with form, fatigue, technique, and individual physiology. Always test under a spotter for true 1RM attempts.