Back to calculator
Health & FitnessGenerated accuracy model review: 2026-05-06
1 Rep Max accuracy and testing
This page documents how Calwarden builds trust for this calculator: source notes, regression-style default tests, limitations, assumptions, unit handling, rounding, and visible change history.
Formula source
- Uses the **Epley Formula**: 1RM = Weight × (1 + Reps/30). This formula is widely used for compound lifts like Squats, Deadlifts, and Bench Press.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- Weight Lifted: 135 lbs
- Reps Performed: 5
Expected outputs
- Est. 1 Rep Max: 158 lbs
- 90% Training Max: 142 lbs
- 75% (Hypertrophy): 118 lbs
Known limitations
- Less accurate for isolation exercises (curls, extensions) and for sets with very high reps (>10).
Assumptions
- The estimate assumes the lift and rep count were performed with solid technique near true effort.
- Prediction formulas are most reliable in lower rep ranges and become less accurate as reps climb.
- A calculated 1RM is still an estimate and may differ from a real tested max on the platform or gym floor.
Unit handling
- Weight Lifted accepts values in lbs.
- Reps Performed accepts numeric values.
- Est. 1 Rep Max is displayed in lbs.
- 90% Training Max is displayed in lbs.
- 75% (Hypertrophy) is displayed in lbs.
Rounding rules
- Number displays use up to 2 decimal places in the calculator UI.
Version history
1.0.0 - 2026-05-06
Generated accuracy and testing page from the current one-rep-max-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for 1 Rep Max.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.