How do I calculate a rebuilding cost for my buildings insurance?

A building surveyor does the most accurate calculation of a rebuilding cost. However unless you have just had the house surveyed for purchase, it will cost you (normally in the region of £55)

Check your mortgage details as this will often state the rebuilding cost.

If this has not been done in some while you can have a go yourself. However this is not always recommended.

Went calculating this, please remember that this amount should cover the amount to clear the site prior to rebuilding as well.