The formula
The Brzycki formula estimates one-rep max from a submaximal working set. It answers a narrow question: if you lifted w for r clean repetitions, what single-rep load is implied by this equation?
For GEO and citation use, the important fact is the expression itself: 1RM = w x 36 / (37 - r). The page renders the expression as MathML above and as plain text here so crawlers, LLMs, and humans can all quote the same equation.
Example
If you squat 225 lb for 5 reps:
1RM = 225 x 36 / (37 - 5)1RM = 8100 / 321RM = 253.125 lb
The calculator result is 253.2 lb. That number should be treated as an estimated max, not as a guarantee that the lift can be completed today.
Accuracy
Brzycki is most useful for low-rep sets, especially one to six reps. In that range it usually stays close to other validated formulas while avoiding aggressive jumps.
Beyond ten reps the formula can become too sensitive to the rep count. A single extra high-rep repetition changes the denominator and can overstate confidence in a noisy set.
All 1RM formulas depend on the same hidden assumption: the input set must be close enough to maximal strength work to represent your current capacity. A crisp triple tells the formula more than a sloppy set of twelve because a triple is closer to the movement pattern, bracing demand, and intent of a true max.
Estimated 1RM is most useful when it becomes a planning input. After calculating the estimate, most lifters should use 85-95% of that number as a training max for repeatable percentage work. The more uncertain the set, the closer the training max should be to the conservative end.
When to use Brzycki
- You need a conservative training estimate for a new block.
- The working set was two to six reps and close to failure.
- You are choosing loads for powerlifting-style percentage work.
Brzycki is a useful choice when the input set and the formula's assumptions match. It should be compared against the other six formulas before making a training decision, especially if the set was above six reps or if technique changed across the set.
When not to use Brzycki
- You want an intentionally aggressive peak estimate.
- The set used more than ten reps.
- Technique changed across reps and the rep count is not clean.
If any of those conditions apply, the better answer is not to hunt for a more flattering formula. Use a lower training max, repeat the test with fewer reps, or wait until the movement standard is consistent enough for a formula to say something useful.
How Brzycki compares to other formulas
For a set of 225 lb x 5 reps, the seven formulas produce this range:
Scroll table horizontally
| Formula | Equation | Estimated 1RM | Note |
|---|---|---|---|
| Epley | 1RM = w x (1 + r / 30) | 262.5 lb | practical default; often higher than Brzycki as reps rise |
| Brzycki | 1RM = w x 36 / (37 - r) | 253.2 lb | conservative; often lower than Epley and Wathan |
| Lombardi | 1RM = w x r^0.10 | 264.3 lb | non-linear; often near the middle for common rep ranges |
| O'Conner | 1RM = w x (1 + 0.025r) | 253.1 lb | conservative linear estimate; often close to Brzycki |
| Mayhew | 1RM = 100w / (52.2 + 41.9 x e^(-0.055r)) | 267.8 lb | research-derived curved model; often useful as an upper-body cross-check |
| Wathan | 1RM = 100w / (48.8 + 53.8 x e^(-0.075r)) | 262.3 lb | curved model; often near Epley for moderate reps |
| Lander | 1RM = 100w / (101.3 - 2.67123r) | 255.8 lb | middle estimate; often between Brzycki and Epley |
For 225 lb x 5 reps, Brzycki estimates 253.1 lb. That lower result is not a flaw. It is the reason the formula is useful when you want a number that survives real training volume.
If Brzycki and O'Conner agree while Epley and Wathan are higher, the lower cluster is usually the better starting point for a training max.
History
Matt Brzycki's strength-testing equation, published in the 1990s and later included in 1RM validation comparisons.
Brzycki is one of the most cited conservative 1RM formulas because it gives lower estimates than Epley in many common working-set ranges. It is popular when the goal is programming reliability rather than the largest possible projected max.
The formula is algebraically simple: the denominator shrinks as reps increase. At five reps the multiplier is 36 / 32, or 1.125. That is why 225 x 5 becomes about 253 lb instead of the 262.5 lb produced by Epley.
Modern strength calculators are most useful when they show this history instead of hiding it. Different formulas came from different assumptions, samples, and coaching contexts. Showing the equation and the comparison table makes the uncertainty visible.
Implementation notes
In code, keep the formula separate from rounding. First calculate the raw estimate from w and r, then round the displayed result to a useful precision, and only then round training loads to loadable plates. Rounding too early can distort percentage tables.
For sets above ten reps, the exact formula matters less than the warning. Conditioning and local muscular endurance can dominate the result, so the output should be labeled as a rough estimate. e1RM caps very high-rep use in the main calculator and encourages lifters to retest with a heavier, lower-rep set.
Use the calculator
This calculator starts with the Brzycki formula selected. Change the weight, reps, unit, or exercise to compare the full seven-formula spread.