According to Harvard University, cycling on a stationary bike at a vigorous pace for 30 minutes burns 315 calories for a 125-pound person, 378 calories for a 155-pound person, and 441 calories for a 185-pound person.
Alternatively, cycling outdoors at 12-13.9 mph burns approximately 240 calories for a 125-pound person, 288 calories for a 155-pound person, and 336 calories for a 185-pound person [ 1
While these estimates can be helpful for some, it’s important to keep in mind that they are estimates and individual energy expenditure may vary depending on sex, age, lean mass, genetics, and other factors.
 (2021). Calories burned in 30 minutes for people of three different weights. Harvard Health. https://www.health.harvard.edu/diet-and-weight-loss/calories-burned-in-30-minutes-of-leisure-and-routine-activities