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Brzycki 1RM Guide

Turn a clean 3-10 rep set into a 1RM estimate accurate to within 3%.

The Brzycki formula converts sub-max rep performance into a one-rep max anchor — no crushing singles required.

Brzycki (1993) fit a simple linear multiplier to sub-max lifting data: 1RM = weight × 36 / (37 − reps). The output is an anchor number that powers every percentage-based program — "75% for 5" only means something when you know the 100%. The math works cleanly between 1 and 10 reps and peaks in accuracy around 3-6 reps, where strength dominates but risk stays low.

Part of: Structural Output

Quick answer

The Brzycki formula converts sub-max rep performance into a one-rep max anchor — no crushing singles required.

What you are trying to do
Turn a clean 3-10 rep set into a 1RM estimate accurate to within 3%.
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 1.00; at 5 reps it is 1.125; at 10 reps it is 1.333.
  • ▸ Valid range 1-10 reps. Above 10, endurance substrate dominates and Brzycki under-estimates 1RM by 10-15%.
  • ▸ Sweet spot 3-6 reps — safe enough to not require a spotter or maximal ramp, heavy enough that strength (not endurance) ends the set.
  • ▸ Training zones fall out of the estimate: ~60% recovery (12-15 reps), ~75% hypertrophy (8-12 reps), ~85% strength (3-5 reps).
  • ▸ Re-test every 4-6 weeks at the same rep count to track true strength change, not formula drift.
  • ▸ Clean reps only — a grinding partial-ROM last rep inflates the estimate by roughly one rep equivalent.

How to

  1. Warm up with 2-3 ramp sets to bring the target load into position-ready range.
  2. Pick a weight you can clean-rep 3-10 times; lower rep counts give tighter estimates.
  3. Enter load and reps into the calculator. Read the 1RM number and the three zone loads.
  4. Program the week off the 75% hypertrophy load as default; add 85% strength work for intermediates.
  5. Re-test at 4-6 weeks using the same rep count you tested at last time.

Examples

  • 225 lb × 5 clean reps
    1RM = 225 × 36 / 32 = 253 lb. Recovery 152 lb · hypertrophy 190 lb · strength 215 lb.
  • 135 lb × 8 bench
    1RM = 135 × 36 / 29 = 168 lb. Program the 75% hypertrophy load of 126 lb for productive 8-12 rep work.
  • 315 lb × 3 squat
    1RM = 315 × 36 / 34 = 333 lb. 3-rep sets live in the Brzycki sweet spot; the estimate is within ~2%.

When to use which tool

▸ Operational Thresholds
  • CYAN · STABLE — 3-6 rep test window — highest accuracy, lowest injury risk.
  • GOLD · GUARDED — 7-10 reps — valid but endurance starts to blur the estimate; expect ±5% drift.
  • MAGENTA · CRITICAL — 11+ reps or grinding partial-ROM last rep — Brzycki breaks; use Lombardi or skip the formula.
▸ Pivot
Max known. Run Wilks to see how efficient that lift is for your bodyweight.
Strength-to-Weight Efficiency · Wilks →

Related

Frequently asked questions

› Why not just test a true 1RM? Troubleshooting

Structural injury risk climbs sharply above 85% for untrained lifters, and a proper 1RM attempt needs a 45-60 minute ramp that wrecks recovery. A 3-5 rep set at 85% gives the same number at a fraction of the risk and cost.

› Is Brzycki better than Epley? Comparison

In the 1-6 rep window they differ by under 1%. Above 6 reps Brzycki under-estimates slightly while Epley over-estimates. For 10+ rep work, Lombardi (weight × reps^0.1) handles the endurance drift better.

› How much does grip affect deadlift estimates? How-to

A lot. Grip-limited deadlift reps report the grip endurance ceiling, not the posterior-chain 1RM. Use straps when testing or exclude deadlift from the formula.

› 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.