One Rep Max Calculator (Brzycki Formula)

About the One Rep Max Calculator (Brzycki Formula)

The Brzycki formula is a common way to estimate a one-rep max from a submaximal set.

Compared with Epley, it tends to give slightly more conservative estimates as rep counts rise. This calculator applies the formula, shows a percentage chart, and lets you compare the result with other common estimates.

It is best used with submaximal sets rather than very high-rep fatigue work.

When This Page Helps

It is useful if you want a conservative 1RM estimate without attempting a true max. The result works best as a programming reference rather than as a literal tested maximum.

How to Use the Inputs

1. Complete a set of an exercise to near failure (2–10 reps recommended).
2. Enter the weight used for the set.
3. Enter the number of reps completed with proper form.
4. View your estimated 1RM from the Brzycki formula.
5. Compare with the Epley estimate shown alongside.
6. Use the percentage chart for training programming.

Example Calculation

Tips & Best Practices

• Brzycki is most accurate in the 1–10 rep range. Above 10 reps, the formula becomes increasingly conservative.
• For safety, many coaches prefer Brzycki over Epley because underestimating max is less risky than overestimating.
• Compare results with Epley — your true 1RM likely falls between the two estimates.
• Test with 3–5 reps for the best accuracy with any formula. This balances between being too close to max (1–2 reps) and accumulating too much fatigue (10+ reps).
• Always warm up thoroughly before a test set, even though you're not testing a true max.
• The Brzycki formula breaks down above 12 reps — stick to 10 reps or fewer for reliable estimates.

The Mathematics Behind Brzycki

The Brzycki equation (weight × 36/(37 − reps)) creates a hyperbolic curve that approaches infinity as reps approach 37. This means each additional rep increases the predicted 1RM by an increasingly large amount, which is why the formula becomes unreliable at high reps. In contrast, Epley's linear formula (weight × (1 + reps/30)) increases the prediction at a constant rate per rep.

Brzycki in Practice

Many collegiate strength programs use Brzycki as their primary 1RM estimation method. Its conservative nature means that when athletes arrive at their programmed heavy singles and doubles, the weights feel achievable rather than overwhelming. This psychological factor — feeling confident under heavy weight — is underrated in training success.

Combining Formulas for Better Accuracy

Sports scientists recommend using the average of 2–3 formulas (Epley, Brzycki, Lombardi) for the most reliable 1RM estimate. This approach smooths out the mathematical biases inherent in any single formula and has been shown to fall closer to actual 1RM in validation studies.

Frequently Asked Questions

• How does Brzycki compare to Epley?

  At 1–4 reps, both formulas give nearly identical results (within 1–2%). At 5–8 reps, Brzycki is 2–5% lower. At 10+ reps, Brzycki becomes significantly more conservative (5–10% lower). Neither is definitively "better" — true accuracy depends on individual physiology. Using the average of both formulas is a common practical approach.

• Why does Brzycki use 36/(37−reps)?

  The numbers 36 and 37 come from Brzycki's regression analysis of strength testing data. The formula implies a theoretical maximum of 36 reps with zero weight (or equivalently, the 37th rep is impossible). This mathematical structure gives the formula its conservative curve at higher rep ranges.

• Is Brzycki more accurate than Epley for powerlifters?

  For competition-trained powerlifters who frequently work in the 1–5 rep range, both formulas are equally accurate because the predictions converge at low reps. However, Brzycki's conservative bias makes it slightly preferred for setting training weights, as it's better to be slightly under your max than over when programming heavy singles and doubles.

• Can I use this for bodyweight exercises?

  You can use it for weighted bodyweight exercises by entering the total resistance (bodyweight + added weight). For unweighted exercises like push-ups or pull-ups, the formula is less applicable because the resistance is fixed and fatigue patterns differ from barbell exercises.

• Should I round the result to the nearest plate?

  Yes, in practice you should round to the nearest loadable increment. Most gyms have 2.5 lb or 5 lb plates as the smallest, so round to the nearest 5 lbs. For training percentages, always round down rather than up for safety.

• How often should I retest?

  Every 4–8 weeks during a progressive program. Many lifters retest at the start of each training block or mesocycle. If your programming uses auto-regulation (RPE-based), you may need to retest less often since the training weights self-adjust based on daily readiness.