How the Epley and Brzycki 1RM estimates work
Estimate an exercise-specific one-repetition maximum from a lifted weight and 1–10 completed repetitions, with separate Epley and Brzycki results and their average.
This page provides an equation-based estimate for education and planning. It does not diagnose a condition, measure an individual response, or replace professional care.
How to use this health calculator
- Choose appropriate inputs: Enter measurements using the units and ranges shown.
- Review the assumptions: Confirm that the model applies before interpreting the result.
- Calculate and interpret: Read the result together with its limitations and cautions.
- Use professional guidance when needed: Do not use a general calculator to change medication, treatment, or a clinician-directed plan.
Formula and variables
Here, w is the weight lifted and r is the number of repetitions completed in one set. For a single repetition, the entered weight is returned. The two equations can disagree because each models the repetition-to-load relationship differently.
Epley 1RM = w × (1 + r ÷ 30); Brzycki 1RM = w × 36 ÷ (37 − r); displayed estimate = (Epley + Brzycki) ÷ 2- w — Lifted weight
- The external load completed for the entered exercise, in kilograms or pounds.
- r — Completed repetitions
- Whole repetitions in one set, limited here to 1–10.
Worked example: 80 kg for five repetitions
A lifter completes five technically consistent repetitions with 80 kg on one exercise.
- Weight
- 80 kg
- Repetitions
- 5
- Epley: 80 × (1 + 5 ÷ 30) = 93.3 kg.
- Brzycki: 80 × 36 ÷ (37 − 5) = 90 kg.
- Average: (93.3 + 90) ÷ 2 = 91.7 kg.
Result: The displayed estimated 1RM is 91.7 kg.
This is a prediction for that exercise under similar conditions—not proof that 91.7 kg can be lifted, a program prescription, or a safe attempt weight.
Understanding your results
Equation result
The numerical output follows the displayed formula and entered assumptions.
Personal interpretation
Individual biology, measurement error, environment, health conditions and medicines can change real-world outcomes.
Assumptions
- The repetitions belong to one continuous set of the same exercise.
- Technique, range of motion and equipment are consistent across repetitions.
- The set was performed with meaningful effort; repetitions completed far from fatigue can understate capacity.
- The entered load excludes body mass unless the exercise and user deliberately account for it.
Limitations
- Prediction error varies with exercise, training experience, fatigue, tempo and individual repetition endurance.
- The Epley and Brzycki equations are population-level shortcuts and are not individualized physiological models.
- An estimate from one exercise must not be transferred directly to another exercise or equipment setup.
- Higher-repetition sets generally introduce more uncertainty, so this calculator limits entry to 10 repetitions.
Common mistakes
- Adding repetitions from multiple sets.
- Mixing pounds and kilograms or changing the unit without changing the number.
- Entering a warm-up set performed far from fatigue.
- Treating percentage-based references as prescribed or inherently safe working weights.
Practical use cases
Educational estimate
Explore how the inputs affect the equation result.
Consistent tracking
Compare estimates only when methods, units and conditions are consistent.
Planning and decision guide
Treat cautions as part of the result
Use suitable technique, equipment, safeties and competent supervision for heavy resistance exercise.
Do not attempt a maximal lift solely because a calculator produced that number. Stop exercise and seek appropriate care for chest pain, faintness, severe shortness of breath, or acute pain.
Escalate symptoms or clinical questions
Seek qualified medical advice for symptoms, diagnosed conditions, medicines, pregnancy, or individualized treatment decisions.
Frequently asked questions
Is estimated 1RM the same as a tested 1RM?
No. It is an equation-based prediction from a submaximal set; an actual test can differ.
Why are two estimates shown?
Epley and Brzycki use different mathematical relationships. Showing both makes their disagreement visible instead of implying false precision.
Can I compare different exercises?
Track each exercise separately and keep technique, range of motion and equipment consistent.
Does the percentage table prescribe training loads?
No. It is arithmetic based on the estimate and does not select appropriate volume, intensity or progression for you.
Sources and review
- Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue — Journal of Physical Education, Recreation & Dance. Accessed 2026-08-03.
- Prediction of 1 Repetition Maximum in High-School Power Lifters — Journal of Strength and Conditioning Research (PubMed record). Accessed 2026-08-03.
Reviewed 2026-08-03.