Fermi estimate: fuel stations operating within San Francisco city limits

Estimate how many gas stations operate in the city of San Francisco. Talk the interviewer through how you structure the estimate, the assumptions you make, the arithmetic, and how you would check that the final number is reasonable. ```hint What makes this city different Before multiplying anything, list the traits of San Francisco that push fuel demand, or the number of stations, above or below what you would expect in a typical American city. ``` ### Clarifying Questions - Does "San Francisco" mean the city and county proper, or the wider Bay Area? - Are we counting stations (sites) or individual pumps? - Should sites that offer only EV charging, or private fueling depots for buses and delivery fleets, be included? - Is the number feeding a decision, such as where to open a station or how fast to roll out charging, and does that call for a point estimate or a range? ### What a Strong Answer Covers - A clear equation, stated before any numbers, linking the city's fuel demand to what one station can supply. - Labeled round-number assumptions that reflect the city's density, car ownership, electric-vehicle adoption and the vehicles that drive in from outside. - Arithmetic with consistent units (vehicles, gallons, days, stations). - At least one independent sanity check and a final range. - Awareness of which assumption moves the answer most. ### Follow-up Questions - Which assumption is your estimate most sensitive to, and how could you get a better value for it in a day? - How should the number change over the next ten years as electric vehicles spread, and what would that mean for a company that owns stations in the city? - A quick look at a map suggests a number very different from yours. How do you reconcile the two?