This is a javascript calculator that will estimate if taking a bus will cost less than what you pay in gasoline. Surprisingly, for short commutes, commuting by car is cheaper than getting a bus pass. (Calculator is on the full article.)

How Much Can You Save on Gas by Riding the Bus?

Fill out this form with our information, and a report will appear below.

Cost of gasolline, per gallon	dollars
Your car's highway MPG	mpg
How long does it take to drive to and from work, in minutes?	minutes
The cost of a monthly bus pas that gets you to work	dollars

Your Report

Your cost to drive to work is approximately $ per day.  If you take the bus, you will break even on the cost of a bus pass at days.  If you ride the bus to work 20 days a month, you will save dollars each month.  (This is the savings after the pass' cost is recovered. A negative value indicates that driving is cheaper than a bus pass.)

This report is calculated by making the assumption that your highway mpg converts to your car's "gallons burned per hour".  If you get 55mpg, then you will burn through 1 gallon per hour if you drive at 55 mph.  If you get 27.5 mpg, then you will burn through 2 gallons per hour if you drive at 55 mph. This is not wholly accurate, but it accounts for the effects of start-and-stop driving common during urban rush-hour.  This effect is negated in hybrid cars with regenerative braking, which get better mileage in the city than regular cars with brake pads.  So this calculator doesn't work for hybrid electric cars. It also doesn't account for attempts at hypermiling.