Costing your glass

In the scenario adjacent, the overall area of the glass would be calculated by multiplying the dimension indicated by the double headed arrows; that is to say, the widest by the tallest.
With a view to trying to reduce the cost of your splashback, you might wish to cut the glass into two pieces at the point marked by the broken line above.
The join would be minimal and you would save on the overall area. To reduce costs even further, you might be able to move the range hood down to the same height as the overheads. The area would then be smaller still and you'd avoid the cost of the corner notches.