Nearly three years ago, I wrote about my compulsion to record the details every time we put gas in the car. At the time, I said, “Mind you, none of this information is of any particular use.”

I’m thrilled to announce that after thirteen years, I’ve finally found value in that spreadsheet. Value beyond soothing the need to collect the numbers, I mean.

Hey, I just realized: since I’ve found a use for the numbers, they’re no longer just semi-random noise. They have meaning! They’re officially information. Data! I’m sure the spreadsheet is very proud.

But I digress.

Anyway, the point is that I have a job. Which requires me to commute. And now I can calculate how much it costs me to go to work.

The bridge toll is six bucks in one direction and zero in the other. And, frankly, that’s the lion’s share of the expense. But, being compulsive, I had to add in the cost of the gas.

One round trip is approximately 35 miles, regardless of which route I take*.

* As I noted recently, crossing the Richmond-San Rafael bridge is essentially a requirement to get from here to there. But there are multiple ways to get from here to the bridge. Since all the routes are functionally the same length, and all the drivers are using the same small group of traffic apps, it’s probably no surprise that it takes the same amount of time to drive all the routes. In this case, about an hour and a quarter. As Bay Area commutes go, that’s staggeringly short for the round trip.

According to my spreadsheet, each dollar we’ve spent on gas has been good for 8.6 miles driven. So one round trip to work costs a hair over four bucks in gas. Add the bridge toll and we get the total price of the trip: ten dollars. No, I’m not compulsive enough to figure in depreciation on the car.

Apply my salary–net, of course–and you get forty-four minutes and a handful of seconds*.

* Yes, I realize that the mathematically astute curious types among you are now busy calculating my pay. Have fun. I’d just appreciate it if you didn’t spread the number around. Make anyone who wants to know go to the effort of punching a few digits into their calculators. And looking up the federal and state withholding percentages. And a few other little deductions that I’ll leave as exercises for the nosy.

With all the approximations I’ve included, you can call it three-quarters of an hour without straining the bounds of mathematics.

Why would I bother with all that math, other than to justify thirteen years of data collection? Well, it turns out that driving is two dollars cheaper than taking the bus. That says more about the cost of public transportation than anything else, but that’s a subject for another time.

More importantly, knowing the cost difference allows me to feel a little better about choosing convenience over saving the environment.