Window replacement cost calculator: how to use one to understand a decision

How window replacement cost calculator works

1. Measure before you type. Walk the house with a tape and write down every opening: width, height, how many sashes and how many of them open. This takes half an hour and it is the difference between an estimate that means something and one that does not. It is also exactly what an installer will ask for.
2. Enter the material you will actually buy. Run the calculation more than once if you are undecided. Comparing the same schedule in uPVC and in aluminium is the most useful single thing these tools do, because the gap between them is stable even when the absolute numbers are not.
3. Flag the awkward openings. Bays, arches, upper floors and anything above a lower roof are the openings that break an average. If the tool has no way to say so, note them separately and treat the output as covering the straightforward windows only.
4. Decide what you want it to include. Some tools estimate supply only, some supply and fit, and some claim to include making good. These are three very different totals. Find the assumption before you compare the answer with anything, particularly with a real quote.
5. Take the schedule to the installers. The schedule you built to use the calculator is more valuable than the calculator's answer. Give the same one to every firm you ask and the quotes that come back can be compared directly, which is normally the only reason the exercise was worth doing.

Insurance and paperwork

Common questions

Should a window replacement cost estimator include VAT?

It should say either way, clearly. A number that is silent about it is ambiguous by a fifth, which is more than most of the differences you are trying to detect between quotes.

Can I use it for doors as well?

Only if it says so. External doors are priced on the door set, the threshold, the frame and the locking, and a tool that treats a door as a large window will understate it.

How close should the estimate be to the real quotes?

Close enough to tell you whether a quote is normal, and not close enough to argue with. If every quote you receive is far outside the estimate, the likeliest explanation is that your house has something the tool could not see.

Registered contractors by region

• Registered roofers in the East Midlands postcode area
• Registered roofers in the East of England postcode area
• Registered roofers in the London postcode area
• Registered roofers in the North East postcode area
• Registered roofers in the North West postcode area
• Registered roofers in the Scotland postcode area
• Registered roofers in the South East postcode area
• Registered roofers in the South West postcode area
• Registered roofers in the Wales postcode area
• Registered roofers in the West Midlands postcode area
• Registered roofers in the Yorkshire and The Humber postcode area