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The Brzycki 1RM Formula

Estimate a true one-rep max from a submax set without risking a heavy single.

Brzycki turns a 3-10 rep set into a one-rep max estimate accurate to within ~3%, with no heavy singles required.

A true one-rep max test requires ramping to failure under a bar that can crush you. Brzycki (1993) showed you can skip that. A well-executed set of 3-10 reps at a known load predicts 1RM within a few percent. The formula is the engine underneath percentage-based programming — every "75% for 5" assumes a 1RM number, and Brzycki is the cheapest way to get one.

Quick answer

Brzycki turns a 3-10 rep set into a one-rep max estimate accurate to within ~3%, with no heavy singles required.

What you are trying to do
Estimate a true one-rep max from a submax set without risking a heavy single.
Best next step
Max Load Capacity · Brzycki 1RM
Limit to remember
Treat this as a practical aid for the task, not a replacement for professional judgment.

Key points

  • ▸ Formula: 1RM = weight × 36 / (37 − reps). At 1 rep the multiplier is 1.0; at 10 reps it is 1.33.
  • ▸ Valid range is 1-10 reps. Above 10, muscular endurance drags the estimate low.
  • ▸ Accuracy is best in the 3-6 rep window — high enough to be safe, low enough that strength dominates over endurance.
  • ▸ Training zones flow from the estimate: ~60% recovery, ~75% hypertrophy, ~85% strength.
  • ▸ Inputs must be clean reps. A grinding last rep with partial lockout inflates the estimate by a rep or two.

Examples

  • 225 × 5 clean reps
    1RM = 225 × 36 / 32 = 253 lb. Strength work at 85% = 215 lb; hypertrophy at 75% = 190 lb.
  • 135 × 8 bench
    1RM = 135 × 36 / 29 = 168 lb. The estimate matters more than the headline — program 75% = 126 lb for productive volume.
  • 315 × 3 squat
    1RM = 315 × 36 / 34 = 333 lb. Tight confidence interval — 3-rep sets are the Brzycki sweet spot.

When to use which tool

Related

Frequently asked questions

› Why not just test a real 1RM? Troubleshooting

Structural injury risk climbs sharply above 85% for untrained lifters, and a single true 1RM requires warm-up ramps that cost an hour and crush recovery. A 3-5 rep set at 85% gives you the same number with a fraction of the risk.

› Is Brzycki better than Epley? Comparison

For 1-6 reps, Brzycki and Epley are within 1%. Above 6 reps, Brzycki tends to under-estimate slightly while Epley over-estimates. The Wathan and Lombardi formulas exist for higher-rep work.

› How should I use this guide with a Kefiw tool? How-to

Use the guide as the plan and the linked Kefiw tool as the check. Read the steps first, try the move manually, then use the tool to compare outputs, catch edge cases, and decide whether the result actually fits your task.

› What mistake do tool guides help avoid? Troubleshooting

Tool guides help avoid using a utility mechanically without understanding what you are trying to accomplish. Most word, writing, and text utilities are fast, but speed can hide context mistakes. Know whether you are solving a puzzle, cleaning copy, drafting a line, or checking a rule.

› Can a tool guide help me learn the skill? How-to

A tool guide can help you learn if you pause before accepting the output and ask why it worked. Compare your first guess with the tool result, look for the rule or pattern, and repeat that review. Passive copying solves one task; active review builds the skill.