You can also use Rabbit, the gear calculator for single speed and fixed. Here, play about with it and it'll tell you what ratios do what for you.
@Bike_Destroyer started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
You can also use Rabbit, the gear calculator for single speed and fixed. Here, play about with it and it'll tell you what ratios do what for you.