You feel good after sex (hopefully). Prepare to feel even better knowing you're doing your body some good.

SuperDrug Online Doctor has created this nifty calculator that will help you determine how many calories you -- and your partner -- burn while doing the nasty.

The calculator takes into account all sorts of variables -- your weight, your partner's weight, position and length of your rendezvous. And it will even equate how many calories of certain foods those are, enabling you to determine just how many French fries your night of passion equaled.

So, while you're in the midst of ecstasy and twisting your body like a pretzel in the pursuit of carnal pleasure the likes of which you only see on Cinemax after dark, take even more pleasure in knowing you're getting a workout that will hopefully be so intense you can knock 10 minutes off the treadmill the next time you go to the gym.

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