The Window to Existing Wall Estimating Calculator should be used to estimate the materials, labour and plant required to fit windows into an existing wall, either as replacements for existing windows, or entirely new openings.

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 Window to Existing Wall Estimating Calculator,  first select a suitable dimensional template, use the picker to select the window, lintel and cavity closer required and then check the dimensional information.

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

  • Frame fixings
  • Plastering
  • Decorating
  • Window Boards
  • Creation/Alteration of Wall Openings
  • Plus all labour associated with the above

To estimate multiple windows of the same size and specification, enter the number of windows when prompted. For example, if you were estimating two 600 x 1200 windows, you would enter 2. This multiplies all Materials, Labour and other associated Resources by two and subsequently doubles the cost.


  • If the size of the opening is changed you must check the suitability of the window, frame and lintel.