What a one rep max is
Your one rep max (1RM) is the heaviest weight you can lift once with good form. Strength programs use it to set training loads as percentages. Testing a true 1RM is tiring and carries some risk, so most lifters estimate it from a set of several repetitions with a lighter weight.
The formulas
With w the weight lifted and r the number of reps:
- Epley: 1RM = w × (1 + r ÷ 30)
- Brzycki: 1RM = w × 36 ÷ (37 − r)
- Lombardi: 1RM = w × r^0.10
The calculator averages the three. With one rep, the 1RM is simply the weight lifted.
Worked example: 185 lb for 5 reps
- Epley: 185 × (1 + 5 ÷ 30) = 216 lb.
- Brzycki: 185 × 36 ÷ 32 = 208 lb.
- Lombardi: 185 × 5^0.10 = 217 lb.
- Average: 214 lb.
- Training loads: 90% = 192 lb, 80% = 171 lb, 70% = 150 lb, 60% = 128 lb.
Same weight, different reps
| Reps with 185 lb | Average 1RM | Epley | Brzycki |
|---|---|---|---|
| 1 | 185 | 185 | 185 |
| 3 | 202 | 204 | 196 |
| 5 | 214 | 216 | 208 |
| 8 | 231 | 234 | 230 |
| 10 | 242 | 247 | 247 |
| 12 | 254 | 259 | 266 |
The formulas agree closely up to about 10 reps. Beyond that, they diverge, because endurance starts to matter as much as strength.
Training with percentages
- 85–95% of 1RM, 1 to 5 reps: maximal strength.
- 70–85%, 5 to 10 reps: strength and muscle growth.
- 60–70%, 10 to 15 reps: hypertrophy and muscular endurance.
- Under 60%: warm-ups, technique and speed work.
Recalculate your 1RM every 4 to 8 weeks as you get stronger, using a set taken close to failure with good form.
Getting an accurate estimate
- Warm up with a few lighter sets first.
- Use 3 to 8 reps: the estimate is most reliable in this range.
- Stop at technical failure, when form breaks down, not when the bar stops moving.
- One lift at a time: estimates for the squat, bench press and deadlift are independent.
Safety
Use a spotter for the bench press and safety bars for the squat. Beginners should focus on technique before chasing heavy loads. If you have a heart condition, high blood pressure or a past injury, check with a doctor or a qualified coach before maximal lifting.