Compare One-Rep Max Equations
Compare two estimated one-repetition maxima from a completed weight and rep count. These are mathematical estimates rather than a measured maximum and can differ with exercise, technique and fatigue.
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Both drift badly above about 10 reps. A true 1RM test is still a 1RM test.
How to use this tool
Enter the weight, repetitions and preferred headline equation. Use a consistent exercise and technically sound set, keeping the weight unit consistent when interpreting the output.
Results and examples
Epley uses weight × (1 + reps/30); Brzycki uses weight × 36/(37 − reps). The 90/80/70% rows are fractions of an estimate, not loads prescribed as safe to attempt.
Worked example
An 80 kg set for five repetitions gives about 93.3 kg by Epley and 90 kg by Brzycki.
Limitations
- High-repetition effects, exercise differences and repetitions in reserve are not modelled.
- The calculator does not recommend attempting a true maximum.
Fields
| Field | Guidance and constraints |
|---|---|
| Weight on the bar | Accepted range: 1–1000 · Input step: 0.5 |
| Reps completed | Accepted range: 1–20 · Input step: 1 |
| Formula | Both drift badly above about 10 reps. A true 1RM test is still a 1RM test. · Epley / Brzycki |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Frequently asked questions
Why do the estimates differ?
They apply different empirical equations to the same set.
Should I immediately lift the 90% value?
No. Personal safety and training circumstances require separate judgement.
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