SIZE DOES MATTER!
Imagine you buy a pair of shoes or boots on the Internet from far away, find they don't fit so your feet hurt and then you have to spend money on returning them or, worse, find the seller will not allow returns.
You don't have to let that happen though.
Thousands of delighted customers buy their footwear online nowadays despite the small risk of wrong sizes in order to get an almost unlimited choice of styles worldwide and truly great prices - especially on otherwise expensive imported brands. For example, the tough but amazingly comfortable and good looking boots from my Aussie boot eBay Store.
How can you reduce that risk of wrong sizes to near zero? By taking a few minutes to learn the basics. It is time well spent.
Shoe sizes are not consistent. Not only do sizes and sizing systems vary from country to country but also within countries - and even different styles made by the same manufacturer or the same style made by the same company in different years may sometimes vary. There are no internationally agreed standards - or even national standards - on shoe sizes so NEVER ASSUME! Tricky huh? You can beat the system though!
Don't be afraid to ask the seller questions. Ask them about the size and fit of the product they are selling and keep asking until you are sure you understand the answers and know your choices.
Try some on if you can. If you can find the right make and style somewhere local, try some on and see what fits. This will also help you with price comparisons - there is no point in sending far away for something you can buy in your own town at the same price - but often you will discover just how much money you can save by buying online.
Check out size charts. Some caution is needed here as these can vary a lot - some are simply inaccurate but most are based on one particular brand or type of shoe which may not work for your choice. Also, be sure you know how to measure your feet to get the right answer from the chart - the difference between a traced outline of a foot wearing thick socks and a bare foot standing on a ruler is a size or two! See below for a link to my own chart.
Beware of the Half Size trap. US sizes go up in half sizes so a US 9 1/2 is half way in length between a 9 and a 10. Width is then measured by letters (from A - narrow - to E - wide) or as 'Narrow', 'Regular' or 'Wide'. UK sizes use 1/2 to indicate a wide fit so a UK 9 1/2 is a wide fitting size UK 9. There is no half size in length in UK sizes - you must often decide whether to go up or down a half size if converting between US and UK sizes.
UK sizes are basically unisex though a lot of footwear manufacturers tend to make their women's and men's sizes a little differently. A rough rule of thumb is that you subtract one number from most US men's sizes to calculate the UK size - so a US men's 10 is usually a UK 9.
US sizes are calculated differently for men's and women's sizes. As a rough rule you subtract 1 1/2 to convert from a US women's to a US men's size so a US women's 8 1/2 is about a US men's 7 in length. Women's shoes tend to be narrower at the heel than men's due to the average difference in foot shape between the sexes.
Australia, New Zealand and some other countries use a hybrid system - men's sizes (and unisex styles) are in UK sizes and women's sizes (except unisex styles) are in US women's sizes. Make sure you know what you are buying.
Most European mainland countries use the Euro sizing system though the sizes can vary somewhat in different parts of Europe and between makers.
Some other countries such as Japan, Russia and Mexico use other systems. Never assume anything!
I specialise in selling top quality Australian made leather boots (Blundstone, Redback, etc) online and for these my chart is as good as you'll find - it won't be very accurate for athletic shoes or even Aussie sheepskin boots such as Uggs though. It will probably give you a reasonable estimate for many other boots and shoes that require a conversion between US, UK and Euro sizes.