Advanced options
Per-window prices are whole-house-job averages (singles cost more alone: mobilisation is real). Bays price like 2.5-3 windows. The trade's structure: national brands quote 30-60% above independent local installers for comparable FENSA-certified work: the "manager's discount if you sign tonight" theatre is priced in from the start. FENSA/CERTASS certification matters (building-regs sign-off + the certificate solicitors ask for at sale). Triple glazing: marginal gain over good double in most UK homes: see our double glazing and secondary glazing pages before spending.
What The Window Replacement Cost Calculator Works Out
- Estimated cost: the number of windows multiplied by the fitted price for your frame and glazing, plus any bays. Whole-house averages run GBP 450-650 a window for uPVC double glazing, GBP 150-250 more for triple, GBP 800-1,100 for aluminium and GBP 1,200-1,800 for timber, so an eight-window semi lands at GBP 4,000-5,500 in uPVC.
- Bay windows: a bay is priced as 2.75 flat windows by default, matching the 2.5-3x multiple every installer's arithmetic uses. Singles cost more than the whole-house rate because survey, mobilisation and scaffold overheads are spread over fewer frames.
- The negotiation reality: 30% of the estimate, which is the typical spread between quotes on identical specs. National brands quote 30-60% above comparable independent installers for the same FENSA or CERTASS certifiable work, and the tonight-only discount is priced in from the start.
- Energy honesty: swapping sound double glazing for new on energy grounds alone pays back over decades. Replace for failed units, rot, security or looks. Misted units can often be re-glazed at GBP 80-120 a pane without touching the frames.
- Bay multiplier (advanced): override the 2.75x assumption if your quote prices bays differently, for example 2.5x for a shallow box bay or 3x for a large Victorian splay.
- Colour / woodgrain foil premium (advanced): coloured and woodgrain uPVC typically adds 10-20% to the frame price, and dual-colour (white inside, colour outside) more. It is purely aesthetic, so the calculator shows it as a separate amount inside the windows-only figure.
- Scaffold or access costs (advanced): a scaffold tower or full scaffold for upper floors, dormers or awkward elevations, added once to the job rather than per window.
- Old frame removal and disposal (advanced): some quotes include taking the old frames away and some charge GBP 15-30 a window. Enter the per-window figure and it is multiplied by every window and bay.
- External doors (advanced): front, back, French and patio doors are usually quoted alongside windows. A composite or uPVC door fitted runs GBP 900-1,500; bifolds and sliders cost far more, so enter their quoted price if you include them.
- All-in cost per opening (advanced): the full estimate divided by every window, bay and door, which is the figure to compare between quotes that itemise differently.
- National brand quote estimate (advanced): your estimate uplifted by 45%, the midpoint of the 30-60% premium national brands charge for comparable certified work. Phasing by elevation, front one year and back the next, keeps the whole-house rate on each half while spreading the spend.