Each year has 365 days. Each day has 24 hours. That’s 8,760 hours a year. Sounds like a lot, but how much of it is spent doing stuff you have to do versus what you want to do?
You need around 8 hours a day for sleep. That leaves 5,840 hours of wakefulness.
A full-time job is around 2,000 hours a year. 3,840 hours left.
In addition to work you’re paid for, you have to run errands and do chores (shop for groceries, go to the bank, yard work, vacuum, cook, wash dishes, etc). Let’s say you average 90 minutes a day on that, which is 548 hours per year. 3,292 hours remaining.
How long is your commute? The average is 25 minutes each way, so just over 208 hours a year. 3,084 hours left.
How long do you take to get ready in the morning? 40 minutes? 240 hours. 2,844 left.
Do you exercise? Maybe you don’t work out every day. 1 hour a day, 3 times a week? 156 hours. 2,688 left.
Now let’s say you’re 25 years old and healthy. According to most actuarial tables, that gives you even odds of sticking around for another 50 years.
2,688 hours * 50 = 134,400 hours. That’s 15 years. I admit it’s a very rough estimate. I left out a lot of factors (such as anything related to raising children). People work less when they’re older, but that’s partially offset by more time spent being sick. I’d also weight calculations toward free time in younger years, since youth usually means fewer responsibilities and greater physical ability. Later years are spent undergoing general cognitive and physical decline.
What wisdom do I take away from this calculation? Pretty straightforward stuff: Find a job you enjoy. Use a tool like RescueTime to ensure you spend your free time wisely. Finally, you spend a significant chunk of your life using your bed, office chair, and/or computer. Don’t skimp on those things.