Many steering wheels are standard sizes, but you can easily measure yours at home before you shop. Start with the diameter (one side to the other). Average sizes are from 14-7.5 inches.
Then measure the thickness of the wheel. Use a tape measure around the wheel grip. These average between 2-4.5 inches.
Since most listings for steering wheel covers include both of these measurements, you are well ahead of the game. Finally, once you’ve made such complicated measurements purchase a tool belt to start your next endeavor.