If you don't have a ruler at home, this website gives you a life size ruler on your screen! There might be other websites and things out there as well so don't worry if you don't have one at home - get creative!
To find the perimeter of a shape, we need to measure the length and width of it first.
For your maths task today, find (or make!) a ruler and measure things around your house. Find at least 5 things to measure - once you have all the measurements, add them together and you will have the perimeter!