Framework for Google Estimation Questions
The Google Estimation question is really 80-95% logic and 5 to 20% math. However, the average candidate gets so worried about the math, they don’t pay attention to the logic. My framework for approaching the estimation question puts logic front and center.
I put the focus on the basic equation and then the logic for how we fill in the variables to reach a basic number.
Tips & Tricks
Variables: No more that 2 to 3 variables for your equation
occasionally a 4th variable is okay if you need to divide for the final answer (think # of servers needed)
Logic For Assumptions: Use logic to fill in values for each variable
Round up or down: You want numbers ending in 0, 2 or 5 because the math is easier.
Think of two solutions before diving in: The follow on question is often, can you think of another approach. If you spend 5 to 15 mins on one approach, it an be difficult to come up with another, so think of two ways before you go too far. (Think: Top Down vs Bottom Up)
Build a cheat sheet of common facts: Think major world populations, size of emails, images, videos, server capacities, etc
A Few Key Steps
Word Problem Approach: Develop an equation with 2 to 3 variables (4 at most)
Sense check: If you can think of another approach before you dive too far in, it will help. They
Use logic to fill in the variables
i.e. US population is ~300M and there are ~100M households so I will assume 25% of 100M households will use my product
Volunteer to question your own assumptions
Break down 1 or 2 of your variables looking at High, Medium and Low Users (as an example) or High, Medium and Low frequency of use, etc.
Review your Logic
Compare your first result to your newly questioned results
Cheat Sheet Example:
US population: 330M
California population: 40M
NYC population: 8M
World population: 7.8B
Size of continental US: 3M square miles
US households: 130M
Average people per household in the US: 3
Life expectancy: 72
Median household income: $65,000
Weight of an average car: 4,000 lbs
Percent of population under 20 or over 65: ~25% (give or take)
Technical
Amazon S3 Standard cost: $0.023 / GB / month
Average file size for a 90-min 720p movie: roughly 3.5GB
Average file size for a smartphone camera picture: roughly 3-5 MB
Average CTR for a search ad: 1.91%
Average landing page conversion rate: 2.35%
Average WiFi bandwidth: ~10Mbps
Cost of iPhone 12 Pro: $999
Cost of Google Pixel 5: $699
Cost of Amazon Echo (4th Gen): $99
General sense of revenue (2020)
Dropbox revenue: $2B
Airbnb revenue: $3B
Google revenue: $181B
Facebook revenue: $86B
Apple revenue: $274B
Amazon revenue: $386B
Netflix revenue: $25B
Google (Alphabet) net income: $40.27 billion
Apple R&D expenditure: $18.75 billion
General sense of user populations
Netflix (Q2 2021): 209 million subscribers
Google G Suite (March 2020): 2 billion+ monthly active users
Uber (Jun 2021): ~1 million drivers in the US
Twitter (Q1 2018): 192 million daily active users
Number of Americans that own a smart speaker (Jan 2020): 60 million
Number of products Amazon sells: over 12 million (not including Amazon marketplace sellers, which brings the total to 350 million)
