You can use the sizing charts below to measure and determine your size per product, per brand:
SixSixOne
http://sixsixone.com/size-chart
Dakine
http://www.dakine.com/CustomerService/ProductFAQ/sizing-charts
Five Ten
http://fiveten.com/templates/jreviews_overrides/views/themes/fiveten/theme_images/sizeconversion.jpg
Leatt
http://www.leatt.co.uk/category/leatt-sizing-chart/
One
http://oneindustries.com/size-chart
Pay careful attention to take your measurements as indicated by the sizing chart to ensure you get an accurate reading. We find the sizing charts are usually spot-on but if the item doesn't fit you, we accept returns. Our return policy can be found here and a step-by-step guide to returning your product can be found here.
Roost Apparel
http://www.roostapparel.co.za/sizing/