The Brzycki Formula: How to Calculate 1RM (With Examples)
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TL;DR: The Brzycki formula — 1RM = weight × 36 ÷ (37 − reps) — is the research community’s favorite 1RM equation, best validated for bench press at low reps. Honest at 1 rep, conservative below 10. Its weakness: the denominator collapses as reps approach 37, so never use it past ~12 reps.
What Is the Brzycki Formula?
1RM = weight × 36 ÷ (37 − reps)
Published by Matt Brzycki in 1993 (Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue). Unlike Epley’s straight line, it divides by a shrinking denominator — beautifully behaved at low reps, mathematically dangerous at high ones.
How Do You Use the Brzycki Formula?
Pounds: bench 225 lb × 5 reps → 225 × 36 ÷ (37 − 5) = 8100 ÷ 32 = 253.1 lb.
Kilograms: squat 100 kg × 5 → 100 × 36 ÷ 32 = 112.5 kg.
Compare with Epley on the same sets: 262.5 lb / 116.7 kg. Brzycki reads lower — more conservative below 10 reps. Our calculator runs both plus five more formulas.
When Is Brzycki Most Accurate?
- Bench press, 1–5 reps: the research community’s preferred bench equation (−3.1 kg mean error on 5-rep loads in D-I testing).
- Any lift at low reps: the curve fits the low-rep strength relationship tightly.
- When you want 1-rep honesty: 100 kg × 1 → exactly 100 kg. No phantom percentage.
What Is the 12-Rep Stability Limit?
As reps approach 37, the denominator (37 − r) collapses toward zero and the estimate explodes. At 20 reps it claims your max is double the weight — obvious nonsense. Never use Brzycki past ~12 reps. Inside its lane it’s excellent; outside, it’s the most dangerous formula of the seven.
| Reps (100 kg) | Brzycki estimate |
|---|---|
| 5 | 112.5 kg |
| 10 | 133.3 kg |
| 12 | 144.0 kg |
| 15 | 163.6 kg |
| 20 | 211.8 kg (absurd) |
Brzycki vs Epley
| Brzycki | Epley | |
|---|---|---|
| Equation | w × 36/(37 − r) | w × (1 + r/30) |
| 100 kg × 5 | 112.5 kg | 116.7 kg |
| 100 kg × 10 | 133.3 kg (identical!) | |
| 100 kg × 1 | 100.0 kg (honest) | 103.3 kg (overshoots) |
| Past 12 reps | Unstable — avoid | Optimistic but bounded |
| Best for | Bench press, low reps | Squat, general use |
They cross exactly at 10 reps. Full head-to-head: 7 formulas compared.
Frequently Asked Questions
Is the Brzycki formula accurate?
At 1–10 reps on compound lifts, yes — among the best-validated, especially bench press. Past 12 reps, no — the math destabilizes. Respect the lane.
How do you pronounce Brzycki?
“Briz-icky” (it’s Polish). Gyms have been butchering it for 30 years; now you know.
Brzycki or Epley for bench press?
Brzycki for sets under 10 — the research favorite for bench, more conservative. For squats or general use, Epley. Or average them via our calculator.
Why does Brzycki give lower numbers than Epley?
Below 10 reps its curve sits under Epley’s line — structurally more conservative. The gap (~4 kg at 5 reps from 100 kg) is normal; neither is “right.”
Sources
- Brzycki, M. (1993). Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue.
- LeSuer, D.A. et al. (1997). “The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift.” Journal of Strength and Conditioning Research, 11(4).