Posted on October 28, 2009 at 11:32pm EDT. More.

Introducing MetroCost

After writing my last post, I realized that I had never formally announced MetroCost on this blog. Well, now is as good a time as any, because until the end of the week I’m giving it away for free!

MetroCost is an app for iPhone or iPod touch that helps you track your public transit expenses. I live in New York City, so I use the subway a lot, but I’m a freelancer, so I don’t ride it every day. I began to wonder: should I really be paying $89 a month for an Unlimited Ride card, or would I save money if I paid $2.25 per ride?

Except it’s not that simple, because if you add $8 or more to a Pay-Per-Ride MetroCard, a 15% bonus is added to your total. As long as you add at least $8 at a time, a ride actually costs $1.96.

So, how does MetroCost help figure this out?

Each time you ride the subway or the bus, launch MetroCost and swipe a finger across the “magnetic” strip. It will keep a record and, based on your average ride count per day, compare the costs of an unlimited versus a pay-per-ride card.

If you’ve recorded 30 days' worth of rides, the calculations will be exact; if you’ve recorded less than that, you will still get a useful estimate. Either way, the next time you need to buy or refill your card, consult MetroCost to see which is best for you.

MetroCost is set up for New York City transit out of the box, but it’s totally customizable. As long as the fare doesn’t vary with distance traveled (sorry, Washington, DC) you can use MetroCost to save money.

You can also frivolously change MetroCost’s appearance to match your transit system’s color scheme.

MetroCost debuted at $1.99 but for this week only you can get it for FREE on the iTunes App Store. On Saturday I’m restoring the price, and maybe raising it, so you’d be crazy not to download it now.

Don’t be crazy!