How to use this calculator
- Enter or choose weight lifted.
- Enter or choose unit.
- Enter or choose repetitions completed.
- The estimated 1RM (average) updates as you type. Use Copy result or Share to keep it.
Method
Epley: 1RM = w × (1 + r ÷ 30); Brzycki: 1RM = w × 36 ÷ (37 − r); shown: the average of the two (a single rep is taken as the 1RM).
- w
- weight lifted
- r
- repetitions completed with good form
Worked example
- Epley: 100 × (1 + 5 ÷ 30) = 116.7 kg.
- Brzycki: 100 × 36 ÷ (37 − 5) = 112.5 kg.
- Average: (116.7 + 112.5) ÷ 2 ≈ 114.6 kg.
Five reps at 100 kg suggests a one-rep max of roughly 113–117 kg, about 114.6 kg on average.
What the result means
Treat the estimate as a planning number, not a target to attempt. The table converts it into common training loads, for example 80–85% of 1RM for sets of about 5–6.
Assumptions and limits
- The set was performed with consistent technique and taken close to muscular failure.
- The equations were developed mainly on trained adults performing barbell lifts.
- Accuracy falls as reps rise; above about 10 reps the equations can be off by 10% or more.
- Results vary by lift and by person: endurance-trained lifters often manage more reps at a given percentage than strength-trained lifters.
Questions
Which formula is more accurate?
Neither is consistently better. They agree exactly at 10 reps; below that, Epley gives slightly higher numbers. Averaging them is a reasonable middle estimate.
Is it safe to test a true 1RM?
Maximal attempts carry injury risk, particularly without a spotter or coaching. An estimate from a 3–5 rep set avoids that risk for most training purposes.
Please note: This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health.