I was 9 years old when my father taught me how to estimate the height of a building using my thumb and simple geometry. As engineers we are taught estimating techniques – in school, and by colleagues and mentors. Quick-and-dirty assessments are indispensable as we engineer new products, and they’re just as critical for product managers exploring new markets and products.
Market sizing is always a chore. But if you think of it as estimating instead of calculating, you'll realize that it's okay to guess.