12 oz cotton duck has a strong, half panama construction, made with single fill yarns and is one of the most popular canvases.
0.67p is the cost of one unit (50cm x 50cm.)
To calculate total:-
1) add 18cm to each of your 2 dimensions (this is to account for the canvas that wraps around the frame).
2) divide the new totals by 50 then multiply together
3) round up the total and this is the number of units that you must purchase.
Eg. stretcher frame is 130cm by 62cm
1) 130+18=148 / 62+18=80
2) 148 divided by 50 = 2.96 / 80 divided by 50 = 1.6
2.96 X 1.6 = 4.736
3) round up to 5
5 units of canvas must be purchased for that stretcher size