Using a Spirit Level check all bench tops and any overheads are level (You may have to make adjustments later)
Widths A and B are the width from the wall to the cooker splashback line, minus 3mm
Height C is the distance 3mm above the worktop minus 3mm where it will meets the cooker hood.
Width D is from the 2 units either side of the cooker hood minus 3mm for each unit so the full width minus 6mm. (if your cooker splashback lines are marked from the edge of the units it will need to be moved in 2mm each side).
Heights E and F are the height you wish your upstands to come to from the horizontal line marked 3mm above the worktop. If you are going full height to your units you need to take an extra 3mm of each where they meet the units.
If two splashbacks or upstands meet at a corner then ensure you also allow an additional 8mm for glass thickness and adhesive depth for one of the pieces (so if 2 pieces meet at a corner, one piece should stop 10-11mm short of the wall to allow for the other piece and an expansion gap- the other piece should be the full distance to the wall minus 2-3mm).
Next to Measure is any power point, always measure to the centre of power point. Typically a cut out of 60×100 is sufficient. But please do check that power point will cover hole in glass.
If you have any further enquires about how to measure a splashback please do not hesitate to contact us, we are more than happy to help.