CalcVitalsOne Rep Max Calculator — Epley & Brzycki
Your one-rep max can be estimated from a hard set: Epley's formula multiplies the weight by (1 + reps ÷ 30). 100 kg lifted for 5 reps gives a 1RM of 116.7 kg — no maximal attempt, and no spotter-risking single, required.
How it works
Testing a true one-rep max is fatiguing, technically risky and disruptive to training — so strength sports estimate it instead. The relationship between reps-to-failure and percentage of maximum is stable enough across lifters that two formulas from the 1980s–90s, Epley's and Brzycki's, remain the coaching standard. Enter a genuinely hard set — one where another rep would have failed or broken form — and both are usually within a few kilograms of the truth.
The percentage table printed with your result is where the estimate earns its keep: programmes are written in percentages (5×5 at 80%, speed work at 65%, a peak single at 92%), and the table turns your 1RM into the actual plates to load. Round to what your plates allow; precision beyond a kilogram is theatre.
Two honest limits. First, the rep relationship differs by lift — deadlift endurance and bench endurance are not the same curve — so use estimates per lift, not one global number. Second, estimates age: recompute from a recent hard set every training block rather than defending an old number your current self cannot lift.
The method
Epley (1985): 1RM = weight × (1 + reps ÷ 30). Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps), valid for reps under 37 and most accurate under 10. Percentage loads multiply the Epley estimate.
Frequently asked questions
Epley or Brzycki — which is more accurate?
They agree closely under about 8 reps. Brzycki tends to read slightly lower on high-rep sets, Epley slightly higher. Averaging the two for sets of 8–12 is a reasonable coaching habit.
How many reps should I test with?
A set of 3–6 reps taken close to failure gives the best balance of accuracy and safety. Singles prove nothing an estimate cannot, and carry the most risk and fatigue.
Does the formula work for every exercise?
Best for the big barbell lifts it was built on. Machine and isolation movements have different rep-to-max relationships and more technique variance — use their estimates loosely, as progression guides.