I have a square table-mat made from rope that spirals from the centre. It is rather like this one:

The mat is a $14$ centimetre square. The rope is $2$ cm wide.

How many centimetres of rope will I need to make another mat just like it?

How much rope would I need to make a $12$ cm square, or a $16$ cm square?

Is there a quick way to work this out?