New York Metrocard Payment Calculator
Instructions: enter the amount currently on your card (you may use the number keys provided on the bottom half of the application) and then hit the calculate button. The amount to add to your card will be highlighted in red. It will also show you the 15% bonus that you get from the mta, the new total amount on the card (starting amount + amount you are adding + 15% bonus). It also shows you how many rides that amount provides.