Free Tool — Personal Training
1RM Calculator (One-Rep Max Estimate)
Estimate a one-rep max from a positive load and a set of 1-10 whole repetitions, then view percentage-based reference loads. The result is an estimate, not a prescription to attempt a maximal lift.
Looking for a NASM 1RM calculator? This is an independent VoltExam tool and is not affiliated with or endorsed by NASM, ACE, ISSA, or NSCA. NASM publishes its own calculator in the source section below.
One-Rep Max Calculator
Enter a whole number from 1 to 10.
Reference Loads (% of Estimated 1RM)
Formula Reference
Epley: 1RM = weight × (1 + reps ÷ 30)
Brzycki: 1RM = weight × 36 ÷ (37 − reps)
For exam practice and estimation only — not a substitute for engineered design, manufacturer data, current codes, or a licensed professional's judgment. Verify all values before relying on them.
How this estimate works
A one-rep max (1RM) is the greatest load completed for one repetition in a specific exercise. This tool estimates that value from a smaller set instead of telling you to attempt a maximal lift.
It calculates the Epley and Brzycki estimates shown in the formula reference and displays their rounded average. Different equations can produce different results, so the output remains an estimate for that exercise and entered set.
ACE says predicted 1RM assessment can be preferable for a novice who lacks experience handling free weights, while actual 1RM testing is not appropriate for every client. NASM likewise describes its calculator output as a ballpark estimate and tells users to prioritize safety.
Primary references
- NASM one-rep max calculator and estimation guidance — the official NASM destination, including its estimate and safety boundary.
- ACE guidance on actual and predicted 1RM assessment — distinguishes predicted assessment from maximal testing and says suitability depends on the individual.
Frequently Asked Questions
Is this the official NASM 1RM calculator?
No. VoltExam is independent and this route is not affiliated with or endorsed by NASM. Use the official NASM destination linked above when you need NASM's own calculator or guidance.
What happens if I enter more than 10 repetitions?
The calculator returns no estimate. This route deliberately limits the input to 1-10 whole repetitions instead of extrapolating a precise-looking value beyond its stated boundary.
Should I use Epley or Brzycki?
This tool shows both formula results and their rounded average. Treat the outputs as estimates; they can differ and they do not decide whether maximal lifting is appropriate for you or another person.
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