The Velux Skylights Estimating Calculator estimates the materials, labour and plant required to fit a Velux skylight in a flat roof. 

To estimate a Velux Skylight, first select a skylight from the Skylight selector then enter the number of skylights. For example, if you were estimating two skylights of the same size and specification, you would enter 2. This multiplies all materials, labour and other associated resources by two and subsequently doubles the cost.

Review the dimensional information for the skylight, paying particular attention to the labour allowed to form the opening and fix the skylight.

The combination of information taken from the specification and the dimensions you enter will be used to automatically calculate the following items:

  • Timber trimmers 
  • Skylight
  • Skylight kerb
  • Skylight fixing kit
  • Plasterboard and finish
  • Decoration
  • Plus the labour associated with the above

This Estimating Calculator is linked to the Specification.


  • The roof waterproof finish is dealt with in the relevant roof Estimating Calculator – either the Rectangular Flat Roof or Universal Flat Roof Estimating Calculator.