Health & Medicine · Fitness · Strength Training
Brzycki One Rep Max Calculator
Estimate your one-repetition maximum (1RM) for any lift using the Brzycki formula based on a submaximal weight and rep count.
Calculator
Formula
w = weight lifted (in lbs or kg), r = number of repetitions performed to near-failure. The denominator decreases as reps increase, reflecting the reduced percentage of 1RM used for higher-rep sets. The formula is most accurate for sets of 1–10 reps.
Source: Brzycki, M. (1993). Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88–90.
How it works
The Brzycki formula is: 1RM = w ÷ (1.0278 − 0.0278 × r), where w is the weight lifted and r is the number of repetitions completed. The denominator decreases linearly with each additional rep, reflecting the physiological relationship between load intensity and maximum volume capacity.
The formula is grounded in the observation that there is a near-linear relationship between the percentage of 1RM used and the maximum number of reps achievable at that percentage. For example, most lifters can perform approximately 5 reps at around 87% of their 1RM. The Brzycki coefficients (1.0278 and 0.0278) were empirically derived to fit this relationship across a large population of trainees.
Beyond estimating the 1RM itself, the percentage breakdown outputs allow athletes to structure periodized programs. Powerlifters use 90–95% loads for strength peaking, 75–85% for hypertrophy blocks, and 60–70% for speed-strength and technique work. This single test set can therefore inform an entire training cycle.
Worked example
Scenario: An athlete bench presses 185 lbs for 8 repetitions to near-failure and wants to estimate their 1RM and training loads.
Step 1 — Identify inputs: w = 185 lbs, r = 8 reps.
Step 2 — Calculate denominator: 1.0278 − (0.0278 × 8) = 1.0278 − 0.2224 = 0.8054.
Step 3 — Divide weight by denominator: 185 ÷ 0.8054 ≈ 229.7 lbs estimated 1RM.
Step 4 — Calculate training loads:
90% = 229.7 × 0.90 ≈ 206.7 lbs (heavy singles/triples)
80% = 229.7 × 0.80 ≈ 183.8 lbs (hypertrophy sets)
70% = 229.7 × 0.70 ≈ 160.8 lbs (volume/endurance work)
This means a set of 185 lbs × 8 reps predicts a 1RM of roughly 230 lbs, and the athlete should use approximately 184 lbs for hypertrophy-focused training blocks.
Limitations & notes
The Brzycki formula is most accurate for sets of 1–10 repetitions. Above 10 reps, the linear model breaks down because muscular endurance and cardiovascular fatigue become dominant factors rather than raw strength, causing the formula to progressively overestimate the true 1RM. The formula also assumes the set is taken to near-failure or true failure; stopping early (leaving reps in reserve) will cause the calculation to underestimate your 1RM. Additionally, the formula was validated on average populations and may be less precise for highly trained powerlifters, novice beginners, or individuals with atypical strength-to-endurance profiles. Results should be treated as estimates rather than definitive maxima, and true 1RM testing should only be performed under proper supervision with adequate warm-up and spotting. The formula does not account for bar speed, rest periods, or exercise technique, all of which influence actual performance.
Frequently asked questions
How accurate is the Brzycki formula compared to actually testing my 1RM?
Studies show the Brzycki formula typically estimates 1RM within 3–7% of the true tested maximum for sets of 1–10 reps. Accuracy decreases significantly above 10 reps. It is best used as a training guide rather than a competition-level number. Factors like fatigue, daily readiness, and exercise selection can all cause variation between the estimate and your actual max on any given day.
Should I use kilograms or pounds with this calculator?
The Brzycki formula works with any unit of weight — it is purely mathematical and the constants do not change. Simply enter your weight in kilograms and interpret all outputs in kilograms, or enter in pounds and interpret in pounds. Just be consistent: do not mix units within a single calculation. The calculator labels outputs in lbs by convention, but the math is identical for kg inputs.
What is the best number of reps to use for the most accurate estimate?
The Brzycki formula is most accurate for sets in the 3–8 rep range. Sets of 1–2 reps can be skewed by technique, adrenaline, or daily variation. Sets above 10 reps introduce muscular endurance as a limiting factor, causing overestimation of 1RM. A set of 5 reps at a challenging but manageable weight is widely considered the sweet spot for reliable 1RM estimation with this formula.
Can I use this formula for any exercise, or just the big three (squat, bench, deadlift)?
The Brzycki formula can be applied to any barbell or machine exercise, including the squat, bench press, deadlift, overhead press, and rows. However, it is less reliable for bodyweight movements or exercises where technique fatigue occurs before muscular fatigue (e.g., Olympic lifts). It is also less commonly validated for isolation exercises like curls or tricep extensions, where rep-to-failure relationships may differ from compound lifts.
How does the Brzycki formula differ from the Epley and other 1RM formulas?
The Epley formula is 1RM = w × (1 + r/30), which tends to produce slightly higher estimates at lower rep counts and lower estimates at higher rep counts compared to Brzycki. Brzycki's linear denominator model is generally considered slightly more conservative and accurate in the 1–10 rep range. Other formulas such as Mayhew, Wathen, and Lombardi each use different mathematical models (logarithmic, exponential, etc.). Research comparing them finds all produce similar results for 1–6 reps, with divergence increasing above 8–10 reps.
How do I use the percentage outputs to design my training program?
The percentage-of-1RM breakdown maps directly to standard periodization zones: 90%+ is used for maximal strength and peaking (1–3 reps); 80–89% targets strength-hypertrophy (3–6 reps); 70–79% is the classic hypertrophy range (6–12 reps); 60–69% supports muscular endurance and volume accumulation (12–20 reps). Many popular programs such as 5/3/1, Texas Method, and Westside Barbell use these zones explicitly, making the 1RM estimate a foundational number for structuring any progressive overload plan.
Last updated: 2025-01-30 · Formula verified against primary sources.