For answering questions like “How many people get a haircut each day in the U.S.?” or “How many diapers are sold in India annually?”

🧠 Step-by-Step Estimation Template

1. Clarify the Question

• "What metric are we solving for?" (e.g. units, $, users, actions/day)
• "What constraints should I assume?" (region, timeframe, user behavior?)

2. Choose a Framework

Use the Fermi Breakdown method:

Break complex questions into smaller pieces with estimates at each step.

Typical breakdown types:

• Population-based: Estimate based on # of people (e.g., diapers sold = # of babies × changes/day × days/year)
• Behavior-based: Estimate based on frequency of actions (e.g., coffees/day/person × # of people)
• Time-based: Estimate based on usage time (e.g., how many YouTube hours watched = users × avg watch time)
• Device-based: Estimate based on devices (e.g., # of smartphones × app usage penetration)

3. Anchor Your Numbers

Use rough but defensible data points (see next section).

4. Multiply Your Way Through