What Is a One Rep Max (1RM)?
Your one rep max (1RM) is the maximum weight you can lift for a single repetition with proper form on any given exercise. It is the gold standard for measuring absolute strength and is used by coaches and athletes worldwide to programme training loads, track progress, and compare performance.
The Epley Formula
This calculator uses the Epley formula (1985), the most widely used 1RM estimation equation:
1RM = Weight × (1 + Reps ÷ 30)
For example, lifting 80 kg for 5 reps gives an estimated 1RM of 80 × (1 + 5/30) = 93.3 kg.
How to Use Your 1RM for Programming
Once you know your 1RM, you can programme your training loads as percentages. Heavy strength work is done at 85–95%, hypertrophy (muscle building) at 65–80%, and muscular endurance below 60%. Most powerlifting and strength programmes use percentage-based loading.
Frequently Asked Questions
Is it safe to test my actual 1RM?
Testing a true 1RM carries injury risk, especially for beginners. Estimating from a 3–5 rep set is safer and nearly as accurate. Reserve true 1RM testing for competition or with an experienced spotter.
How often does my 1RM change?
Beginners can see strength gains weekly; intermediate lifters monthly; advanced athletes may take 3–6 months per meaningful improvement. Recalculate your 1RM after each training block (typically 4–8 weeks).
Which formula is most accurate — Epley, Brzycki, or Lander?
Studies show minor differences; all formulas are most accurate at 3–5 reps and less accurate above 10 reps. The Epley formula tends to slightly overestimate at high rep ranges, so use lower reps for better accuracy.
Medical Disclaimer: This calculator is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for health decisions.