The Roof Windows Estimating Calculator estimates the Materials, Labour and Plant required to fit a roof window.

This Estimating Calculator is linked to the Specification. Therefore many of the items required for the window are specified from the Specification you have chosen.

To complete an estimate in the Roof Windows Estimating Calculator, you enter dimensional information into the Worksheet.

The combination of resources taken from the Specification and the dimensional information will then calculate the following items automatically:

  • Frame fixings
  • Plastering
  • Decorating

To estimate multiple windows of the same size, enter the number of windows when prompted. For example, if you were estimating three 660 x 1180 roof windows, you would enter 3. This multiplies all Materials, Labour and other associated Resources by three and consequently increases the cost threefold.


  • Before accepting the output, you should check all the pre-specified items, and in particular any items that are highlighted in red to show that they are “critical items” which are listed in the Resources Output screen.
  • If the size of the opening is changed you must check the suitability of the selected window and frame etc.
  • In addition to the pre-specified items you must also carefully scrutinise the bottom section of the Resources Output screen. This section covers the more freeform aspects of the window such as the window type, trimmers and the labour for fixing the various types of window, which are not necessarily directly linked to the dimensions you have entered.