Do some math (or get Google to do it for you)
If I were to stereotype myself, I would tell you that I'm a language guy, not a math guy. I can do math, but—and I say this unashamedly—I use a calculator to get it done and get it done right. Did you know you can use Google search to do calculations for you? Not surprisingly, it will do simple stuff like 2+2, 12x12, and the like. It'll do more complex things, too. Check out these examples:
On the Google search page, simply type in your equation. E.g., 8000 * 3.66667. On the results page you should see the calculator appear with the answer to your equation.
More complex math
It'll do more complex math than that, too. Let's say you want to know the square root of 14 to the 3rd power. Type: sqrt(14)^3 and press enter.
Oh, it will do unit conversions, too. How many feet in a mile? Type "1 mile in feet" (w/o quotation marks) and press enter.