Anchors and Benchmarks

Great estimators carry a mental toolkit of reference numbers. A million seconds is about 11.5 days; a billion seconds is roughly 31.7 years. The US economy runs in the tens of trillions of dollars a year, and Earth's population is about 8 billion. These anchors make any Fermi problem easier.

Build your own list. Know your city's population, your country's area, the rough cost of gas and a loaf of bread. Every anchor you memorize is a new starting point for an estimation chain.

The best estimators also feel the orders of magnitude between scales. Confusing millions with billions is a thousand-fold error — like mistaking a house for an aircraft carrier.