Well personally, I just go for ones that feel right as soon as I try them on, wearing the thick socks that I always wear with them. Walk about the shop with them on and if they rub of feel tight anywhere then don't buy them. They should fit quick snugly with thick socks.
I love my walking boots. I would wear them all the time if I could.
No, it isn't. Your feet need more room in a walking boot because you should wear thicker socks. These absorb sweat and provide a cushion against stones and other lumps and bumps in the ground. Ideally, you should wear a pair of thin plus a pair of thick socks, if you're doing some serious walking. When you go to choose boots, take with you the socks that you will wear when you will be out on the hills and fields.
When you buy running shoes (I replace mine about every 600 miles - so that's about twice a year) ... they tell you to buy a size bigger than your shoe size, because ...
(1) they tend to "come up small" and
(2) you need to allow for your feet to expand when you run (gross, I know)
So I always think -
(1) Why don't manufacturers make their running shoes the right size, instead of "a bit small"?
(2) Why don't they allow enough room for wearers' feet to expand when they run? (it's reasonable to assume that someone who buys running shoes" might, perhaps, "run" in them!)
bookbinder is right, with walking boots you usually wear thicker socks, they protect from getting too many blisters, too small, then your feet will get very cramped, and make matters worse.
I have good boots for walking, but the socks i have are are thick proper walking type, warm and toasty
Go to a specialist shop, you will be measured and fitted properly, they also have slopes built for you to walk up and down. A good shop will also tell you to wear them in the house for a short period and if they are not comfortable you can take them back. I have a pair of Brashers in my normal size and they are like weaing slippers
Wear your walking socks and try the boots on, they probably will stretch with time but not much. Running shoes are sized normally because most people who buy them don't run at all, including me. I have just retired my Gola 2 stripes to be slippers now the sole and upper has parted!!
If you get your boots fitted they tell you that almost everyone wears walking boots which are too small for them. They need room to allow for your feet to expand as they get hot and they also need space so that when you are coming down hill your toes do not touch the front of the boot. If they do you will get blisters. To test the size tap your tow on the ground with your foot evrtical - if you can feel the front of the boot they are too small.