How do l measure my horse for a saddle and can l buy one online and it fit my horse?

If you put it in as a search there is a video that shows you. You should be able to fit four fingers stacked under the pommel and on top of the wither. Best to get a saddler to fit you up then you know it will fit.

Measuring a horse for a saddle is somewhat similiar to measuring yourself for a pair of shoes. An average size horse (and an average sized foot) might work out okay this way. Anything out of the ordinary is going to be tough - they do not fit many saddles (or feet) & buying online is almost impossible.
And just as one size 7 might be too large for ur feet, & another size 7 too small, so it goes with saddles. One semi-Quarter horse tree can be totally different than another semi-QH tree. There r a number of different brands & makes, & they can vary in lengths, angle, width, etc. This is true whether u r looking at Western or English saddles.
If u want to buy a saddle on-line, l would suggest u do ur homework as much as possible. Try the exact brand & make of saddle if u can. See how it fits both u & ur horse. This is tough, but it sure will help if u can do it. Also, try to talk to seller & see what info u can get - perhaps they can measure the horse they owned that best fit that saddle & that information will help u know how it will work with yours.
Also, be aware that it is almost impossible to judge quality of leather & saddle unless u see it yourself, or personally know the brand. One person is idea of ''Good quality leather'' might be simply that it is not broken or torn, another person might feel it must be smooth, soft, supple & thick. l have seen many cheaper end saddles bought off the internet that r basically nothing more than a piece of water buffalo hide tacked onto a poorly made frame. My saddlemaker showed me one that was bought off the internet that had pieces of chipboard tacked in to make it wider. You could see the board under the leather bottom. Not good.
If u can buy a saddle cheap enough that u wo not lose much money, it might be worth the while IF it is a good brand name so it will resell. If u buy a cheap saddle & it turns out to be awful, selling it is rather difficult. You r going to have to either lie, or else find a truly naive seller who wo not ask the right questions about it - it if just does not fit any horse, is cheaply made, has broken pieces, who is going to want to rebuy it from you?
So l would be very careful going this route. For some people it works; if they buy a well known brand of saddle, ask lots of questions, do not pay too much, & try the saddle elsewhere if possible. Good luck.

Buying an unseen saddle is always a risk. Measure ur horse like this. take a strong piece of wire about 3o inches long. Mold it to ur horse from the middle of the withers. Lay the wire mold on cardboard & draw the line, cut out the cardboard. Now u can measure the width & height (from the widest part of the wire) of the cardboard. This will give u the measurements, to match to the gullet height & bars of any saddle. If u find a saddle online, ask for the measurements, & u should be pretty close to a perfect match. Here is a pic for you, scroll to the bottom.
http://safesaddles.com/faq/fitting.php

it is a little boring, but it is accurate.

http://statelinetack.com/horsetraining/htl_intro.asp

hope it helps! & it is not a good idea to order online. if u get the measurements & go to a tack store, ask them if u can try the saddles on ur horse. if they say yes, try to trailer ur horse & bring him there. that way u know it fits & u do not have to make tons of trips. however, of ur horse is easy to fit, then make sure u can return the saddle, whether u buy it in a store or off the internet.

You can get here many types of saddle in reasonable price at http://agritura.com/index.php/cat/c1_Horse---Rider.html/category/Horse---Rider . Before 6 month, l had get English Saddle from this site. Its very comfortable for Horse Riding, Hunting, Jumping. l love this saddle.