We all have our habits that cost small amounts of money that eventually add up. If you want to find out just how much you'll spend on them every year, there's a quick way to find out:
Estimate the weekly cost of each purchase. If it costs $4 and you do it four times per week, then the weekly cost is $16.
Add two zeros to the end. In this example, we get $1600.
Divide that number by half. Here, we get $800. This will be a rough approximation of the yearly cost.
Strictly speaking, this will actually give you the cost of 50 weeks of the habit, though it's reasonable to assume there would be some variation throughout the year, anyway. It's also a great way to get a frame of reference for how much you might be able to save by changing certain habits.
Of course, the great thing about math is that there's no limit to the number of quick, time-saving shortcuts that can be useful in daily life. We're sure you've got plenty more, so share them in the comments below.