One Rep Max CalculatorFree online fitness & health calculator — instant results, no sign-up
Estimate your 1RM and training loads.
For general information only. This is not medical advice, diagnosis, dosing guidance or a treatment recommendation. Talk to a doctor or other qualified health professional about your health, pregnancy, or diet.
Sign in to save results and favorites.
About the One Rep Max Calculator
This calculator estimates your one-rep maximum (1RM)—the maximum weight you can lift for a single repetition—using a completed submaximal set. It calculates estimates using both the Epley and Brzycki equations, alongside target training loads at 90%, 80%, and 70% of your estimated maximum.
- Weight lifted
- The amount of weight lifted during the set, entered in kilograms (typically between 1 and 500 kg).
- Reps
- The number of completed repetitions performed with that weight before failure (typically between 1 and 36 reps).
Formula and method
Epley 1RM = w × (1 + r / 30) Brzycki 1RM = w × 36 / (37 − r) 90% Load = Epley 1RM × 0.90 80% Load = Epley 1RM × 0.80 70% Load = Epley 1RM × 0.70
- wWeight lifted in kilograms
- rNumber of repetitions completed
The tool computes two separate 1RM estimates: the Epley formula models a linear increase of roughly 3.33% of base weight per rep, while the Brzycki formula uses an inverse linear scale. Submaximal training percentages (90%, 80%, and 70%) are calculated directly from the Epley 1RM, and all outputs are rounded to one decimal place.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Weight lifted100 kg
- Reps5
Results
- Epley 1RM116.7 kg
- Brzycki 1RM112.5 kg
- 90%105 kg
- 80%93.3 kg
- 70%81.7 kg
How to use the One Rep Max Calculator
- 1Enter the weight lifted in kilograms for a completed set.
- 2Enter the number of full repetitions achieved with good technique.
- 3Evaluate the calculated Epley and Brzycki 1RM values to establish your estimated ceiling.
- 4Use the 90%, 80%, and 70% loads to plan working sets for strength or hypertrophy training blocks.
Reading your result
The Epley and Brzycki numbers provide a realistic range for your single-rep peak strength without requiring an actual maximal attempt. Because the Brzycki formula scales down slightly quicker at moderate repetitions, it often yields a slightly more conservative estimate than Epley. The submaximal load percentages help determine appropriate weights for multi-rep working sets.
Limitations
These equations lose accuracy as repetition counts exceed 10 to 12 reps, where endurance and fatigue resistance overshadow raw maximum strength. The Brzycki equation cannot be evaluated at or above 37 repetitions because the denominator reaches zero or becomes negative. The calculator also does not account for exercise selection, lifter experience, or lifting tempo.
Common questions
Which formula should I follow: Epley or Brzycki?+
Neither formula is definitively superior; lifters often treat the Brzycki output as a conservative baseline and the Epley output as an upper-end estimate for heavy compound lifts.
Why does the calculation become less reliable at high rep counts?+
Sets above 10–12 repetitions rely heavily on anaerobic endurance, muscle fiber fatigue tolerance, and cardiovascular conditioning rather than absolute force production.
Why are the 70%, 80%, and 90% loads based on the Epley formula?+
The underlying program code calculates percentage-based working loads directly by multiplying the Epley 1RM by 0.70, 0.80, and 0.90 respectively.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
You might also like
BMI Calculator
Body mass index with category, healthy weight range, BMI Prime and Ponderal Index.
Calorie Calculator
Daily calories to maintain, lose or gain weight.
Body Fat Calculator
Estimate body fat using the U.S. Navy tape method.
BMR Calculator
Basal metabolic rate with Mifflin-St Jeor and Harris-Benedict.
Ideal Weight Calculator
Ideal weight from four well-known formulas.
Pace Calculator
Running pace, speed and finish time.
Results are estimates for informational purposes and are not financial, medical or legal advice.