One Rep Max Estimate Calculator
Estimate one-repetition maximum from a recorded low-repetition set using the stated Brzycki relationship.
YOUR CALCULATION
Result
—
Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Apply the rational Brzycki convention to the recorded load and completed repetition count.
Estimated1RM=36×load/(37−repetitions)
Worked example
A 60 kg set for 5 completed repetitions gives an estimated 1RM of 67.5 kg. One completed repetition returns the recorded load.
Assumptions and input details
Use1–10 recorded repetitions from a consistent exercise and technique. The relationship is a prediction model, with exercise-specific and individual error. It does not measure a maximum or establish a safe training load. Percentage rows are arithmetic only; this tool does not instruct you to perform a maximal attempt or a fatigue test.
References: Brzycki 1993: author-uploaded original paper
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
The 19 mass definitions distinguish avoirdupois and troy measures, metric and regional measures. Japanese kin is 600 g; mainland Chinese shijin is 500 g.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
Find the heaviest symmetric plate load that fits your inventory without exceeding an entered target.
Aggregate sets, repetitions and external-load volume by exercise label.
Convert pounds, kilograms, ounces, stone and explicitly identified ton and troy units.
Reserved advertising space.