If you don’t have one, here is a tape measure you can download and print: https://z5d9i3t2.stackpathcdn.com/wp-content/uploads/2020/11/measuringtape-A4.pdf
Like human clothing, not all sizing of dog coats and jumpers are the same – your dog may be a large in one brand and a small in another so measuring is important.
Firstly, measure your dog’s chest and add 2”/5cm for wriggle room.
Trouser suits – These are measured slightly differently, please check their category listing for a measuring guide.
Coats and jumpers usually, but not always, have a back length measurement. Take your tape and start measuring from just below where their collar would sit to the base of their tail (where their tail joins their body).
Sometimes your dog will fall between sizes. If this is a chest measurement, then go up in size. If it’s the back measurement then, round down in size if your dog’s tail stands up and round up in size if their tail points down.