In our modern, mostly-metric-unless-you-live-in-the-US world, unit conversions are a part of life. Inches to centimeters. Pounds to kilograms. Dollars to Euros. With Yosemite, you can perform these simple conversions quickly and easily using the revamped Spotlight search tool—no Google search or third-party app required.
Pop open Spotlight, either via the Spotlight menubar icon or by pressing command-spacebar, then type in your query. Easy, right?
How specific you need to be depends on your query. For example, when I type “$12,” Spotlight automatically gives me the exchange rates for US Dollars to Euros, as well as exchange rates between the US Dollar and the Canadian Dollar, the British Pound Sterling, the Japanese Yens, and the Swiss Francs. for any other exchange rates—say, between the US Dollar and the Mexican Peso—I need to be more specific.
Spotlight handles unitary conversions for various measurement standards, including time, temperature, mass, volume, and length. Give it a try and see for yourself what it can do.