The calories you burn stretching really depend on how long and rigorously you go at it. A relatively active stretching session where you move postures every minute or so, such as in a Hatha yoga class, burns about 149 calories in 30 minutes for a 155-pound person.Because larger people have more mass to move around, they burn more calories than smaller people. relatively active stretching session where you move postures every minute or so, such as in a Hatha yoga class, burns about 149 calories in 30 minutes for a 155-pound person. Because larger people have more mass to move around, they burn more calories than smaller people.