Horse Rug Size Conversion Chart

I was just wondering if this horse rug size conversion chart was fairly accurate, and would like to hear of anyones experiences with using size conversion charts when buying horse rugs.

http://www.horsesuppliesdirect.com.au/webcontent11.htm

Take the cm sizes and divide them by 2.5, that'll give you the measurement in inches.

Thanks, but can you buy a rug depending on the high according to this chart. Say I got a 16.1hh horse could I find the rug size according to the size of the horse and then order a rug that was according to this chart 6'6. Would it fit etc?