Window Replacement Cost Calculator

Replacing windows is one of those jobs where the quote and the mental estimate rarely match, because people price the windows and forget that fitting them costs about as much again.

The arithmetic is simple: Total = Number of Windows × (Price per Window + Installation per Window)

That is the whole calculation. What makes budgeting hard is not the maths, it is that both numbers move enormously with choices you have not made yet.

What drives the window price Glass count is the headline. A single pane is the cheapest and worst; double pane is the default in most of the developed world; triple pane costs roughly twice a double and earns its keep in genuinely cold climates and almost nowhere else. Beyond that, frame material (vinyl, wood, fibreglass, aluminium-clad), the coating package, gas fill, and whether the window is a stock size or made to order all move the figure. A made-to-order arched window in a heritage frame can cost five times a stock double-hung of the same area.

What drives the installation price Access is most of it. A ground-floor window in an ordinary opening goes in quickly. A second-storey window over a conservatory roof needs scaffolding, and that scaffolding costs the same whether it serves one window or six, which is why replacing all the upstairs windows at once is usually far cheaper per unit than doing them one at a time.

The other variable is what the installer finds when the old unit comes out. Rotten sill framing, failed lintels, or lead paint turn a two-hour job into a two-day one. Ask whether the quote covers remedial work or excludes it, because “excludes it” is the common answer and the difference lands on you.

Using the calculator Enter your own per-window and per-install prices rather than a national average, because averages hide exactly the variation described above. If you have a written quote, use its numbers and the calculator becomes a way to test scenarios: what does dropping from triple to double pane save across twelve windows, or what happens if you do the upstairs this year and the rest next.

One thing worth checking before you commit. Get at least three quotes, and compare the per-window figure rather than the total, since installers bundle differently and a cheap-looking total sometimes covers fewer units than you assumed.