Could also try using something similar to this pricing calculator - there are many different ones available http://www.craftfairsuk.com/craft-calculator.aspx
On this patterns the black area is what you cut and throw away. Just be careful though because there are also patterns where the black is kept and the white area is cut out lol
Beautiful work and fabulous execution.
The piece is by an artist called Narya Blackfyre and can be contact through either http://naryablackfyre.deviantart.com/art/I-love-my-demons-471964049or https://www.facebook.com/Naryablackfyreart
Thanks for all the lovely comments. Not sure of the frame yet as it is to go into sons bedroom but will drop in to my brother's Art Gallery and framing business to see what he has and will work.