Double glazing cost calculator: what the job involves and who is registered to do it

How double glazing cost calculator works

1. Give it the opening count, not the room count. The single input that matters most is how many separate apertures there are and how many of them open. Counting rooms understates a bay and overstates a landing with one small fixed pane, and a calculator fed room counts will be wrong in both directions at once.
2. Set the frame material honestly. Material is the biggest single multiplier in any estimate. Running the same house as uPVC, aluminium and timber shows you the real shape of the decision far better than any brochure, and it is the comparison a calculator is actually good at.
3. Treat access as a separate question. Very few calculators ask about upper floors, conservatory roofs below windows, or a frontage on a busy pavement. All three change how the work is done. If your house has any of them, treat the output as a floor rather than a figure.
4. Ignore any output that includes making good. Reveals, sills and plaster are property specific and no calculator can price them. If a tool claims to include them it has assumed a standard house, and older properties are where that assumption breaks hardest.
5. Use the number to shortlist, then get it measured. The right use of an estimate is deciding how many firms to ask and what to ask them, not deciding what to pay. A measured survey against a written schedule is the only number that binds anybody.

Insurance and paperwork

Common questions

Why do two calculators give me different answers?

Because they assume different specifications and different amounts of builder's work. Neither is lying; they are estimating different jobs. Read what each one says it includes before comparing the outputs.

Can a calculator tell me if a quote is too high?

It can tell you a quote is a long way outside the normal range, which is worth knowing. It cannot tell you a quote is too high for your house, because the reasons a house costs more are the ones the form never asked about.

Do I have to give my details to get an estimate?

Not for a genuine estimate. If a tool will not show a number without a phone number, what you are using is a lead form with a calculator on the front, and the number that arrives later is a sales call rather than an answer.

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