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An opening size measures the space the glass must fit. A glass size measures the finished pane. They differ because channels, hinges and seals take up room. On every shower and bath layout you give us the opening and the configurator takes the allowances off for you. On other products the field labels say which figure they want. Never take an allowance off yourself and then let the configurator take it off again.
Keep a survey record first
Write down the top, middle and bottom widths separately, both side heights and both diagonals. Measure from finished surfaces, including tiles where the glass will meet them. Our measuring pack has a record sheet for this.
Use the smallest width and the smaller height when you order, but keep every reading. If the diagonals differ by more than 3 mm, the opening is out of square: write both down and tell us when you order rather than averaging them. A big difference between the top and bottom widths, such as 902 mm against 896 mm, is worth telling us about too.
Shower and bath glass: give the opening
The configurator asks for the opening, or the width from the wall on a screen with a free end, plus the height you measured. It then works out each pane and shows the breakdown line by line, starting with your figure and ending with the glass size. These are the allowances it takes off:
| Where | What comes off |
|---|---|
| A glass edge in a wall U channel | 5 mm off the width |
| A panel standing in a U channel | 3 mm off the height |
| A hinged door or hinged bath panel | 8 mm off the height, for the seal along its bottom |
| Hinges and seals between panes | The hinge gap and seal for that layout, taken once |
| A free edge with no fitting | Nothing |
Two fields are the exception and say so on screen. Door width and Hinged panel width are the finished glass width of that pane; the fixed panel beside it takes what is left of the opening. On the fixed panel with a door hinged to the wall, the field is Finished glass height and nothing is taken off it.
Where a layout's allowances are still being confirmed, the sizes are labelled provisional and our team checks them before cutting. You then press "Confirm these measurements" on the size step.
Other products
| Product | Which figure |
|---|---|
| Shelf in an alcove | The opening, said to be an opening, or 3 mm to 5 mm under the smallest width |
| Mirror between two cabinets | The space, less 3 mm at each side |
| Mirror on an open wall | The size you marked out |
| Table top | The finished size: the base plus the overhang |
Each product guide explains its own figures, for example how to measure for a glass shelf and how to measure for a fixed shower screen.
Check the drawing against your notes
The configurator draws your exact pieces as you type. Compare each labelled dimension with your survey, looking from the same side. A pane that looks right in 3D can still be the wrong size. If you already have finished glass sizes from a fitter, say so before you order, and check they are not reduced again.
If the wall bows, the glass meets an obstruction, or a size is marked provisional, send us your readings and the layout. A photo helps explain the space but cannot replace measured sizes. For a survey we carry out, use measuring visits. For the final check, read drawings and checks. For help, contact the team with your reference.
Questions we get asked
Should I take the channel off before entering a shower opening?
No. Give the opening as measured. The configurator takes the channel, hinge gap and seals off once each and shows you the breakdown.
Is the door width the gap or the glass?
The glass. Door width is the finished glass width of the door, and the fixed panel takes what is left of the opening.
Can I send just the narrowest measurement?
Enter the smallest width, but keep all three readings and the diagonals. They show us a taper or a bow the fittings may need to take up.
Does a drawing confirm that my wall is square?
No. A drawing shows the sizes you gave us. Check your survey and the drawing together before you approve it.
Contact the team with your order reference and the step you need help with, or search all help topics.