You can sweat it out on a Spin class stationary bike that literally goes nowhere. You can simulate riding over hills and flat roads, or riding through winds, all with the turn of a knob that changes the resistance of your ride. You'll also pile on some cycling miles, just like you would on the open road. The exact distance you cover depends on your speed and pedaling power.
The official Spin site claims a person pedaling at an average rate of 80 to 110 revolutions per minute for a 40-minute class covers approximately 15 to 20 miles. Based on this estimate, you’ll cover between 22.5 and 30 miles in an hour if you go at an incredibly aggressive rate.
Just as you slow down on hills outdoors, adding resistance to simulate hills indoors also slows you down. The Spinning organization recommends you ride hills at a cadence of 60 to 80 rpms, or revolutions per minute. When you simulate climbing hills, this slower pace means you cover about 75 percent of the distance you would on flat land going 80 to 110 rpms. A class that features mostly hills, or consists of one long hill climb, is equal to about 16 to 20 miles out on the road instead of 22.5 to 30.
Most classes feature a blend of hills, flats and wind sprints. The more fit you are, the faster you can attack the obstacles and the farther you’ll end up going. The only way to track the exact distance is to find a bike with an attachable device that tracks miles ridden. These aren't standard accessories, but could be worth your investment since they can also track heart rate and calories burned.
Your goal in an indoor cycling class isn't to cover a specific number of miles, but to get a high-quality workout. If you're pedaling at a very fast speed with little resistance, you may cover a lot of "miles," but you aren't challenging your strength or your heart rate. If your butt is bouncing in the seat and you're moving your legs faster than 120 rpms, you probably have too little resistance. Go at a rate that puts you into a moderate- to high-training zone and your mile numbers won't matter.