calories burned

Has anyone else noticed the massive range of calories you apparently burn for the same exercise? I did 30 minutes of Kettlebells yesterday and according to one web site calculator this burned 114calories, according to another it burned 500! Both sites used my weight, type of exercise and duration to calculate this.

There's no wonder people get so confused and upset when they don't lose weight because if they trusted the second figure this entitles them to a slice of pizza, whereas the first figure gives you 1 small chunk of cheese.