We have a cheap sofa in Ds's room, the bastard cat has scratched it so the foam is popping out, can't afford to replace it so would like to cover it, I was thinking of getting some cheap fabric from ikea. How much do I need (as in how do I measure, don't expect some random internet person to know) and assuming I can't get a piece wide enough can I wonderweb it together ? I just want to make a large throw I suppose , nothing complex.