How the 1RM calculator works
Enter a weight you lifted and how many reps you managed, ideally a hard set with good form. The calculator estimates your one-rep max with two well-known formulas:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
The big number is the average of both. Estimates are most reliable between 2 and 8 reps and get less precise above 10.
Using percentages to train
Once you know your 1RM, you can choose weights for any goal. The table under your result lists common percentages and roughly how many reps most people can do at each:
- Strength: 85–95% of 1RM for 2–6 reps
- Muscle (hypertrophy): 65–85% for 6–12 reps
- Muscular endurance: below 65% for 15+ reps
Weights are rounded to 2.5 kg (or 5 lb) so they match real plates.
Tips for an accurate estimate
- Warm up properly before your test set.
- Use a set close to failure, finishing with one or two reps left at most.
- Keep form strict. Bounced or half reps inflate the estimate.
- Test when fresh, not at the end of a long session.
Getting stronger from here
Use your numbers inside a structured plan. The workout split builder gives you sets and reps by goal. Add a little weight whenever you reach the top of your rep range. Eat enough protein with the protein calculator. For technique feedback by video, our coaches can review your lifts.
Limitations
1RM formulas are estimates. Results vary by individual, exercise and training experience. Always lift with good technique, use safety equipment such as pins or a spotter, and stop if you feel pain.
