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Concept

Build-Measure-Learn loop

The Build-Measure-Learn loop is the core engine of the Lean Startup: turn a hypothesis into the smallest product that can test it, measure how real customers respond, and learn whether to persevere or pivot, as fast as possible.

Ries drew the loop as three arrows, but he insists it is planned backwards. You start from what you need to learn, work out what you would have to measure to learn it, and only then decide what to build. Read forwards, the loop tempts founders into building first and finding a metric later, which is how a year disappears into features. The point of the loop is speed of the whole cycle, not of any one stage: a beautiful product that takes six months to reach a customer is a slow loop, and a landing page that reaches a hundred customers by Friday is a fast one. Each turn should end in a decision, which is why the loop connects directly to the pivot-or-persevere meeting. A startup that completes many loops learns more than one that completes one big build, even if the big build is better engineered.

A real-life example

A two-person team in Ankara wanted to sell an inventory tool to pharmacies. Instead of building, they measured first: they asked twelve pharmacists to photograph their stock counts for a week, then built a spreadsheet that flagged expiring products. The pharmacists who kept sending photos told them which feature the software actually needed. Three loops later they had a product; the first version they had sketched was never built.

How to use it

  1. 1Before building anything, write the learning goal and the measurement first, then let those decide the smallest build.
  2. 2Measure the length of one full loop in days. Your job is to shorten it, not to make any stage more elegant.
  3. 3End every loop with a written decision: persevere, adjust, or pivot. A loop without a decision is a demo.