What is the Brzycki equation?

The Brzycki equation (1993) estimates one-rep max as: 1RM = Weight × 36 / (37 − Reps). It's a linear model that's most accurate for 1–6 rep sets.

How accurate is the Brzycki formula?

For sets of 1–6 reps, the Brzycki formula is typically within 3–5% of actual 1RM. Accuracy decreases with higher rep counts, particularly above 10 reps.

Why does Brzycki differ from Epley?

Brzycki uses a linear model while Epley uses a slightly different approach. They agree closely at low reps but diverge at higher reps, with Epley giving higher estimates. The divergence table shows exactly how they separate.

Should I use Brzycki or Epley?

Use Brzycki for lower-rep strength work (1–6 reps) where it's most accurate. Use Epley if you regularly train in the 8–15 rep range. For the most reliable estimate, average two or more formulas.

Brzycki Equation Calculator

Name: Brzycki Equation Calculator
Author: Manish Kumar

Formula	Est. 1RM (kg)
Brzycki	112.5
Epley	116.7
Lombardi	117.5
Mayhew	119
Wathen	116.6
O'Conner	112.5

%1RM	Weight (kg)
100%	112.5
95%	106.9
90%	101.3
85%	95.6
80%	90
75%	84.4
70%	78.8
65%	73.1
60%	67.5
55%	61.9
50%	56.3

Reps	Weight (kg)	%1RM
1RM	112.5	100%
2RM	109.4	97.2%
3RM	106.3	94.4%
4RM	103.1	91.7%
5RM	100	88.9%
6RM	96.9	86.1%
7RM	93.8	83.3%
8RM	90.6	80.6%
9RM	87.5	77.8%
10RM	84.4	75%
11RM	81.3	72.2%
12RM	78.1	69.4%
13RM	75	66.7%
14RM	71.9	63.9%
15RM	68.8	61.1%
16RM	65.6	58.3%
17RM	62.5	55.6%
18RM	59.4	52.8%
19RM	56.3	50%
20RM	53.1	47.2%

Reps	Brzycki (kg)	Epley (kg)	Difference
1	100	100	0
3	105.9	110	+4.1
5	112.5	116.7	+4.2
8	124.1	126.7	+2.6
10	133.3	133.3	0
12	144	140	-4
15	163.6	150	-13.6
20	211.8	166.7	-45.1

Key Takeaways

The Brzycki formula (1RM = Weight × 36 / (37 − Reps)) is most accurate in the 1–6 rep range, making it ideal for strength-focused training.^[1]
Compared to Epley, Brzycki produces lower estimates at higher rep ranges (10+), reflecting a more conservative prediction that many coaches prefer.^[2]
The divergence between formulas increases with rep count — at 1–5 reps, all major formulas agree within 2–3%, but at 15+ reps they can differ by 10%+.^[3]

The Brzycki Formula

Matt Brzycki published this equation in 1993 as a linear model for estimating one-repetition maximum:

1RM = weight × 36 / (37 − reps)

The formula assumes a linear relationship between weight and rep count — each additional rep requires a reduction of approximately 1/36 (≈2.78%) of the 1RM. This makes it mathematically elegant and easy to invert for training load calculations.^[1]

For a general 1RM calculator that uses multiple formulas, see the One Rep Max Calculator. For RPE-based loading, try the RPE to 1RM Calculator.

When to Use Brzycki vs Other Formulas

Use Brzycki when: working in the 1–6 rep range, programming percentage-based strength training, or when you prefer conservative estimates.

Consider Epley when: working in higher rep ranges (8–12+) where the Brzycki formula may underestimate true 1RM due to its linear nature.

The divergence table shows exactly how the two formulas separate as rep count increases, helping you choose the right model for your training style.

For specific rep max targets, see our 3RM Calculator, 5RM Calculator, or 10RM Calculator.

Limitations and Important Notes

The Brzycki formula breaks down mathematically at 37 reps (division by zero) and becomes unreliable above 10–12 reps.
All 1RM formulas assume consistent rep speed and full range of motion. Partial reps or variable tempo will skew results.
Exercise-specific factors (e.g., squat vs. bench press) are not captured — 1RM accuracy varies by movement pattern.
This tool is for informational and journaling purposes only. It does not constitute personalized advice.

Frequently Asked Questions

Sources & References

Strength testing: predicting a one-rep max from reps-to-fatigue. Brzycki M. J Phys Ed Rec Dance (1993)
Comparison of 1-RM prediction equations. Various. PMC (2012)
Validation of 1RM prediction equations in trained and untrained subjects. Various. J Strength Cond Res (2014)

Manish Kumar

Certified Personal Trainer & Sports Nutritionist

NASM-CPTCertified Sports Nutritionist10+ Years Experience500+ Clients Coached

NASM-certified fitness and nutrition coach with over 10 years of hands-on experience helping people build strength, lose fat, and live healthier lives. Specializing in gym-based workouts with a strong focus on lifting technique, biomechanics, and practical exercise science. Through FitLifeRegime, sharing the tools, tips, and insights that have worked for hundreds of clients — helping you start your own fitness journey with confidence and clarity.

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Certified Personal Trainer & Sports Nutritionist from the National Academy of Sports Medicine

This tool is for informational and journaling purposes only.

I am NOT a doctor.

Brzycki Equation Calculator