This calculator is a helpful estimate, but is just a guide to give you a basic idea of how much paint is required. It’s accurate but some measurements (like excluding windows, doors, recesses etc) will affect the results a bit. Happily, we offer super-fast delivery if you fall short- and returns if you over order. it. If you’d like some more help calculating your requirements get in touch with our friendly team: info@graphenstone.co.uk