One-Rep Max Calculator
Your one-rep max (1RM) is the most weight you could lift for a single repetition with good form. This calculator estimates it from a lighter set you have already performed, so you do not need to test a true max lift to program your training.
Fill in the form and select Calculate to see your result here.
What is 1RM?
Rather than risking injury testing a true one-rep max, lifters commonly estimate it from a set of multiple reps performed with good form near failure, using an established prediction formula.
1RM Formula
This calculator uses the Epley formula, one of the most widely used 1RM estimation equations in strength training, most accurate when the set performed is 10 reps or fewer.
1RM = Weight × (1 + Reps ÷ 30)
1RM Example
Lifting 60 kg for 8 reps: 1RM = 60 × (1 + 8 ÷ 30) = 60 × 1.267 ≈ 76 kg.
Approximate % of 1RM by Rep Range
| Reps | % of 1RM |
|---|---|
| 1 | 100% |
| 2-3 | 93-95% |
| 5 | 87% |
| 8 | 80% |
| 10 | 75% |
| 12 | 70% |
How to Use This Calculator
- Perform a set of a lift with good form, ideally close to failure but well short of true max effort.
- Enter the weight you lifted and the number of reps you completed.
- Select "Calculate" to see your estimated 1RM and common training percentages of it.
Limitations
- Accuracy decreases noticeably above about 10 reps, since the relationship between reps and load becomes less linear at higher rep counts.
- Individual fatigue resistance varies — two lifters with the same estimated 1RM may have different true maxes.
- This is an estimate for programming purposes; always use a spotter and safe equipment for any genuine max-effort attempt.
Frequently Asked Questions
It is one of the most widely used estimation formulas and is reasonably accurate for sets of 10 reps or fewer performed near failure. It becomes less reliable for higher rep sets.
Many strength programs prescribe working weights as a percentage of 1RM (e.g. 80% for 8 reps) — see the reference table above for common rep-to-percentage relationships.
Only with proper warm-up, a spotter or safety equipment, and solid technique — many lifters rarely need to test a true max and can program effectively from estimated values instead.