So Tesco's King Edward potatoes say they contain 173 calories per 100g... But Sainsbury's King Edward potatoes only claim to contain 81 calories per 100g. I'm so confused - why the big difference? Surely they are both potatoes!!!

just checked the websites, Sainsburies is cooked weight, tescos is raw

But surely there is more calories per 100g after cooking because cooking removes water, making the potatoes lighter? So in that case there should be more in the Sainsbury's ones than the Tesco ones.
The Tesco nutritional info is for the potatoes "when roasted according to instructions"... So it sounds like they are cooked as well anyway.

Well if Tesco are roasted, according to instructions, maybe there is fat as well?

I have the calorie density of potatoes as 440 calories per pound. I will have to do the maths to turn that into metric!

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Boiling potatoes removes some of the starch, so less calories. Baking potatoes concentrates it so more calories for the same weight. The variety of potato and where it is grown can also effect the calories. A pound is 454 grams if that helps. There are 2.2 pounds in a kilogram.