How many calories does 2 minutes of sit ups burn?

When it comes to burning calories, how hard and for how long is much more important than what you do. Pretty much all activities that gives you the same increase in heart rate for the same time will burn the same amount of calories.

Now, it can be a bit difficult to get a good burn going doing sit-ups only, as most people won't have enough upper body endurance to keep doing it fast and long. And it's dependent on weight, gender, age, fitness level etc.

But let's say you can do sit-ups at a pace that gets you about as sweaty and winded as if doing aerobics, then you'd need something like 15-20 minutes of continuous sit-ups to burn around 200 calories.