Rep Max Calculator (Epley vs Brzycki)
Estimate your 1RM and compare Epley and Brzycki formula results from any set.
How to use this tool
- Enter weight lifted and reps performed in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your epley 1rm estimate and the full breakdown beneath it.
Compare the two most commonly cited 1RM estimation formulas: Epley (weight × (1 + reps/30)) and Brzycki (weight × 36 / (37 − reps)). Both are most accurate for sets of 1–10 reps. For heavy sets of 3–5 reps, the two formulas are very close; they diverge more at higher rep counts.
Formula
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Average: (Epley 1RM + Brzycki 1RM) ÷ 2
How it works
This calculator estimates one-repetition maximum (1RM) strength from a submaximal set using two widely cited regression formulas. The Epley formula (1985) is linear and slightly overestimates at higher rep counts; the Brzycki formula (1993) uses a slightly different hyperbolic structure and tends to give closer results at lower rep counts. Presenting both alongside their average allows you to assess the range of uncertainty.
Both formulas are most reliable for sets of 1–10 reps; accuracy drops considerably beyond 10 reps because fatigue mechanisms beyond that range are not well captured by simple linear or near-linear equations. Always warm up properly before any maximal or near-maximal effort.
Worked example
Worked example
- A lifter completes 5 reps with 100 kg.
- Epley: 100 × (1 + 5 ÷ 30) = 100 × 1.1667 = 116.67 kg.
- Brzycki: 100 × 36 ÷ (37 − 5) = 3600 ÷ 32 = 112.5 kg.
- Average: (116.67 + 112.5) ÷ 2 = 114.58 kg.
Epley 1RM = 116.67 kg; Brzycki 1RM = 112.5 kg; Average = 114.58 kg
Key terms
- One-repetition maximum (1RM)
- The maximum load that can be lifted for exactly one complete repetition with correct form; the standard measure of absolute strength in a given exercise.
- Epley formula
- 1RM = weight × (1 + reps/30); a simple linear equation proposed by Boyd Epley that tends to slightly overestimate 1RM at higher rep counts.
- Brzycki formula
- 1RM = weight × 36 / (37 − reps); developed by Matt Brzycki; closely matches the Epley formula at low rep counts but diverges as reps approach 37 (its mathematical asymptote).
- Submaximal testing
- Estimating strength capacity from a set performed below maximum effort; safer than true maximal testing and useful for tracking progress during a training cycle.
- Rep range accuracy
- The reliability of 1RM predictions decreases as the rep count rises; 3–6 rep sets generally give the most accurate estimates with these formulas.
Frequently asked questions
- When do Epley and Brzycki diverge most?
- At higher rep counts (8–10+), Brzycki tends to give a slightly lower estimate than Epley. For 1–5 reps, the difference is usually less than 5%. Use the average as a conservative estimate.
- Which formula should I use?
- Either is fine for most purposes. Epley is more widely cited; Brzycki is algebraically equivalent to the Lombardi formula. The best approach is to track your estimated 1RM over time using the same formula.