Please, please, please. Do yourself a favor and check the manufacturer or sellers sizing chart and measuring instructions. Do exactly as it says for that manufacturer or seller.
NEVER use another manufacturers or sellers measuring instructions!!!
NEVER use what you think your size is from another article from some other manufacturer.
NEVER assume you know what size you are just because that is what you have worn in the past.
It's really quite simple. Find the Manufacturers or sellers measuring instructions and use a tape measure. If you don't own a tape measure visit your local fabric shop or sewing center and buy a good one. Heck, it's only a couple of bucks.
For the Scotweb Balmoral Argyle Tweed Jackets the measuring instructions can be found as a link on this page.
http://www.scotweb.co.uk/sr_swhdr_tw...ll?display=all