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Health and fitness formula

How to calculate brzycki one-rep max

The Brzycki formula estimates a one-rep max from a submaximal set.

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Direct answer
Formula
1RM = weight * 36 / (37 - reps)

Use the table below to match each symbol with the right input. Keep units consistent before you start.

Brzycki one-rep max formula
Start here when you only need the equation and variable names.
Formula
1RM = weight * 36 / (37 - reps)

The Brzycki formula estimates a one-rep max from a submaximal set.

Variable meanings
Check each symbol, meaning, and unit before you calculate.
SymbolNameDescriptionUnit
1RMOne-rep maxEstimated maximum weight for one rep.weight
weightLifted weightWeight used for the set.weight
repsRepetitionsCompleted reps with the lifted weight.Depends on inputs
When to use this formula
Check that your situation matches the formula before you trust the result.
  • Helpful for strength planning when reps are in a low to moderate range and form was consistent.
Step-by-step method
Follow these steps when you are solving it by hand.
  1. 1Use the weight lifted for a hard set.
  2. 2Use the number of completed reps.
  3. 3Keep reps below 37 so the denominator stays positive.
  4. 4Treat the result as an estimate, not a guarantee.
Examples
These sample numbers show the order of operations and units.
Five-rep set
weight
100 kg
reps
5
  1. 1.1RM = 100 * 36 / (37 - 5)
  2. 2.1RM = 3600 / 32
  3. 3.1RM = 112.5 kg
Result
The estimated one-rep max is 112.5 kg.
Eight-rep set
weight
185 lb
reps
8
  1. 1.1RM = 185 * 36 / (37 - 8)
  2. 2.1RM = 6660 / 29
  3. 3.1RM = 229.7 lb
Result
The estimated one-rep max is about 230 lb.
Mistakes to avoid
Small input or unit errors can change the answer a lot.
  • Treating the brzycki one-rep max result as a diagnosis or a personal training plan.
  • Mixing inches, centimeters, pounds, and kilograms without converting first.
  • Using stale measurements after weight, activity, or training level changes.
  • Ignoring the method assumptions behind the estimate.
Open the One Rep Max Calculator
Open the calculator for the answer without rewriting the formula.

Enter your values in the related calculator, then compare the output with the hand method above.

Open One Rep Max Calculator
FAQs
Short answers for common formula questions.
Is the Brzycki one-rep max formula a medical test?

No. It gives an estimate from a few inputs. Treat it as a planning or screening number, and ask a qualified clinician about symptoms, medication, pregnancy, eating disorders, or medical conditions.

Why can my Brzycki one-rep max result differ from a wearable or lab test?

Different methods use different assumptions. Small measurement changes, activity estimates, and rounding can move the result.

Can I use the One Rep Max Calculator instead?

Yes. The One Rep Max Calculator handles the arithmetic and helps catch unit conversion mistakes.