Fermi Estimate: Sizing America's Yearly Gas Expenditure

Estimate how much money is spent on gas in the United States over one year. Lay out the structure of your estimate, label each assumption, and finish with a figure and a range you would stand behind. ```hint Pick the quantity you price Choose the physical quantity you will multiply by a price, such as gallons, and decide whether to reach it through vehicles and miles driven or through households and how often they fill up. ``` ### Clarifying Questions - Does "gas" mean gasoline sold for vehicles, or should natural gas used for heating, cooking and power also count? - Should the total include businesses and government fleets (delivery vans, work trucks, rideshare driving), or only what households spend? - Is diesel in scope alongside gasoline? - Should the price be today's pump price including taxes, or an average over the past year? ### What a Strong Answer Covers - A scoped definition of "gas" and of whose purchases count, settled before any arithmetic - A top-line equation that links vehicles or households, fuel use and price per unit - Labeled, round assumptions, each with a short rationale - Correct, unit-consistent arithmetic that is easy to follow - A sanity check from a second angle, a final range, and the inputs that drive it ### Follow-up Questions - Which assumption moves your answer the most, and how would you tighten it? - How would the figure change over the next decade as more electric vehicles join the fleet? - What would you add to the estimate if the interviewer wanted diesel and natural gas included?