How many calories you'll burn while working on a stationary bike depends on what your current weight is, how fast you're pedaling and how long your workout lasts. You also can maximize your exercise time on the bike with additional exercises and speed drills. No matter what style you choose, invest in a heart monitor if your bike doesn't already have one, so you can safely burn calories while in your target heart rate zone.
Biking at moderate speed means you've found a nice, middle-ground pace: not too fast, not too slow, and you can still conduct a conversation with someone. At this pace, you can burn 200 to 300 calories during every 30 minutes of exercise, depending on your weight. The heavier you are, the more excess fat you have to burn, so your calories burned will be higher. As you lose weight, you'll burn fewer calories for the same amount of exercise.
Pedaling at an accelerated speed naturally will burn more calories than a medium pace. You may not be able to converse normally without breathing hard during a vigorous bike workout. If you weigh 200 pounds, you can burn more than 400 calories in 30 minutes with a fast-paced session on an upright stationary bike.
These stationary bikes allow you to recline and rest your back against a padded chair-type seat as you pedal. Recumbent bikes are even lower-impact than upright models. While they are excellent for someone with back, hip or knee problems, their design keeps your torso still, so you burn fewer calories than if you were pedaling on an upright bike with moving handlebars. The exception to this is if you focus on foot position and work with different speeds and inclines; if you use a pro-active method with your recumbent bike exercise, your calories burned will be consistent or higher with those burned on an upright bike.
Whether you have an upright or recumbent machine, your workout can be pushed farther with the bike's computer options, such as changing the simulated terrain. This means you can set the bike to ride up and down imaginary hills and provide you with the corresponding resistance. Most bikes have preset courses you can start, or you can plan your own as you go by pressing the controls to ramp up or tone down the resistance.
There are other ways you can add to your stationary bike workout, such as upper body exercises with weights or spinning, which is a cardiovascular workout done on your bike, complete with resistance switch-ups and changes in position, from sitting to standing and back again. An hour-long spinning class can burn between 500 and more than 1,000 calories, depending on your weight and workout intensity.