Estimation question

How would you estimate the number of monthly users for Dropbox?

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Estimation methodology: can you reason from a plausible top-down anchor to a defensible number with clearly stated assumptions.

Pick an anchor: global internet/smartphone users, roughly 5 billion (state as assumption).
Estimate the share that are likely knowledge workers or students who'd need cloud storage, e.g. 20%, giving about 1 billion addressable.
Estimate Dropbox's share of that addressable market against competitors (Google Drive, OneDrive, iCloud), e.g. 5-8%.
Multiply through: 1B x 6% = ~60 million monthly users, and sanity-check against known public figures for scale.
Cross-check with a bottom-up angle: businesses using Dropbox Business plus individual free-tier users, to see if the numbers roughly agree.
State what real data (public filings, app-store estimates) would replace the assumptions.

Uses a top-down market-share approach and states every assumption as a number the interviewer can push back on.
Cross-checks with a second, bottom-up method (business seats + individual users) rather than relying on one approach alone.
Reasons explicitly about competitive share against Drive/OneDrive/iCloud, since that's the real constraint on Dropbox's number.
Lands on a round, defensible final number and states the confidence range, not false precision.

Pulling a market-share percentage from nowhere with no comparison to competitors.
Not cross-checking the top-down estimate against a second method.

Chapters of the AI PM course that teach what this question tests.