One Rep Max Calculator
Estimate maximal strength from a safe submaximal set of 1–12 repetitions.
Your One Rep Max Result
Result status:
Practical interpretation
Important: Estimate only—not medical advice.
How the One Rep Max Calculator works
Formula: Epley 1RM = weight × (1 + reps ÷ 30). Brzycki comparison = weight × 36 ÷ (37 − reps).
The primary result uses Epley. Brzycki provides a comparison, and 90%, 80%, 75%, and 70% Epley loads support training planning.
Assumptions and limits: Prediction error grows as fatigue and repetitions increase; do not attempt a maximal lift without suitable experience and safety controls. Results are estimates for education and planning, not medical advice.
How to use your result
Use the result as a starting point, not a pass-or-fail score. Keep your inputs consistent, observe relevant trends over time, and adjust only when the trend—not one day—shows the estimate does not fit your needs.
Body measurements and equation-based targets always contain uncertainty. If your result conflicts with symptoms, a diagnosis, medication guidance, pregnancy needs, an eating-disorder recovery plan, or instructions from your care team, follow your qualified health professional.
Frequently Asked Questions
What does the One Rep Max Calculator calculate?
It estimates estimate epley one-rep max, compare brzycki, and view training percentages.. The result is an educational planning estimate rather than a clinical assessment or guaranteed performance outcome.
What formula does the One Rep Max Calculator use?
Epley 1RM = weight × (1 + reps ÷ 30). Brzycki comparison = weight × 36 ÷ (37 − reps). The full method and assumptions are displayed above the references.
Can I enter metric or imperial measurements?
Yes. Imperial mass and height entries are converted to kilograms and centimeters before calculation, while results use your selected display system.
How accurate is the One Rep Max Calculator?
It is best used as a starting point. Prediction error grows as fatigue and repetitions increase; do not attempt a maximal lift without suitable experience and safety controls.
How should I use the result in training or nutrition planning?
Apply it conservatively, keep inputs and measurement conditions consistent, and use multi-week trends in performance or body weight before adjusting your plan.
When should I recalculate?
Recalculate after a meaningful change in body weight, training performance, activity, or another required input—not in response to normal day-to-day fluctuations.
Who should seek individualized guidance?
Minors, pregnant people, competitive athletes with specialized demands, and anyone with an injury, medical condition, or eating-disorder history should consult an appropriately qualified professional.
Is this result medical advice?
No. The calculator cannot account for a diagnosis, medication, injury, laboratory result, or instructions from your health care team.
Scientific References
- The accuracy of prediction equations for estimating 1-RM performance Journal of Strength and Conditioning Research
- Progression models in resistance training for healthy adults American College of Sports Medicine position stand
- ACSM Guidelines for Exercise Testing and Prescription American College of Sports Medicine