Double Glazed Windows Cost Calculator | UK Price Estimate | PTF Glass
Not sure how much your replacement double glazing is going to cost? Our cost calculator gives you an instant estimate based on your window sizes and glass type — so you can go into a quote conversation knowing roughly what to expect.
Enter your window details below and get a UK price estimate in seconds. All estimates are based on our 2026 supply-only pricing for made-to-measure sealed units.
How to Use the Calculator
The calculator works in three steps:
- Enter the number of windows you need to replace. You can do one unit or a whole house — the calculator handles both.
- Choose the approximate size for each window. If you’re not sure of the exact measurements, pick the closest size category. Small covers most standard casement windows; bay and large covers wider panels. You’ll need to measure accurately when you order, but the calculator gives you a working estimate.
- Select your glass type. Standard clear glass is the most affordable. Low-E (low emissivity) glass is slightly higher but significantly improves energy performance. Tinted, solar control, and obscure glass options are also available.
The estimate you get is a supply-only price range — that’s the cost of the glass unit itself, manufactured to measure. Fitting costs are separate and vary by installer and location.
What Affects the Cost of Replacement Double Glazing?
The two biggest cost drivers are size and glass specification. Here’s what each means in practice.
Window Size
Double glazed sealed units are priced by area. A small standard casement (around 600 × 900mm) costs significantly less to replace than a large bay panel or a floor-to-ceiling patio door light. If you have a mix of sizes across your property, the calculator totals them accurately.
Glass Type
Standard clear float glass is the baseline. Low-E glass — which has a microscopically thin metallic coating that reflects heat back into the room — costs a little more but meaningfully improves thermal performance, particularly on north and east-facing windows. Obscure glass for bathrooms and privacy applications falls in a similar price range. Tinted or solar control glass is available for south-facing windows where glare or heat gain is an issue.
Frame Compatibility
The unit thickness needs to match your existing frame’s rebate depth — typically 20mm, 24mm, or 28mm. The wrong thickness won’t seat properly in the beading. If you’re not sure what thickness you currently have, measure the existing unit from edge to edge or ask a glazier to check. PTF Glass advises on thickness when you request a quote.
Number of Units
Replacing multiple units in the same order can reduce per-unit delivery costs. If you have several windows that need replacing — misted units in different rooms, for example — it’s worth batching them into one order.
Is the Estimate Accurate?
The calculator gives you a reliable price range based on our standard 2026 supply pricing. For most standard rectangular sealed units in clear, low-E, or obscure glass, the estimate will be close to the actual supply-only price.
The estimate won’t be exact if your unit is:
- Non-standard shape (arched, angled, triangular) — these require bespoke manufacture and carry a premium
- Very large or unusually proportioned — bay and door panels vary significantly by exact dimensions
- A specialist specification, such as laminated safety glass or acoustic glass
For any of these, the calculator still gives you a useful starting point — but an exact quote requires your actual measurements. Use our free measure and quote service for confirmed pricing before you order.
Why Order Replacement Sealed Units from PTF Glass?
PTF Glass manufactures sealed units to measure and supplies direct to homeowners and trade. You get the same supply-only pricing whether you’re a glazier placing a trade order or a homeowner replacing one cloudy pane.
- Made to measure: Every unit is manufactured to your exact dimensions — width and height in millimetres. No off-the-shelf sizes that don’t quite fit.
- Fast turnaround: Standard units are typically ready within 3–5 working days. We dispatch nationally.
- Full glass range: Standard float, low-E, tinted, solar control, obscure, and more — all available in the correct thickness for your frame type.
- Trade and homeowner supply: No trade account required. Homeowners get the same supply-only pricing as the glaziers they’d otherwise go through.
- Free measure and quote: Not sure about your measurements or specification? Our free quote service confirms everything before you order.
Frequently Asked Questions
Do I need to measure the glass or the frame?
Measure the glass — not the frame opening. The unit needs to match the existing sealed unit that’s being replaced. Measure width and height in millimetres from edge to edge of the glass panel itself, and note the unit thickness (the distance from front to back, typically 20mm, 24mm, or 28mm). If you measure the frame opening instead, you’ll get a unit that’s the wrong size.
Can I use the estimate to organise my budget before getting a quote?
Yes — that’s exactly what it’s designed for. The calculator lets you work out a realistic budget range before you commit to a quote. Once you’re ready to order, get a confirmed price through our quote service so you have exact figures to work from.
Does the calculator include fitting costs?
No. The calculator shows supply-only pricing — the cost of the sealed unit itself. Fitting is a separate cost that depends on who installs the unit, the property location, and the difficulty of access. Most glaziers charge £50–£150 to fit a unit you’ve supplied. If you’re practically minded, a standard rectangular unit is something competent DIYers fit successfully — there are no specialist tools required beyond a glazing tool or suction cup for handling large units.
What if I have an unusual or non-standard window?
Contact us directly via the quote form. We manufacture non-standard and bespoke units — arched, angled, triangular, and oversized panels — and can advise on specification and pricing once we have the dimensions. The calculator is designed for standard rectangular units, so unusual shapes need a manual quote.
How long will the replacement unit last?
A quality sealed unit typically lasts 15–25 years before the edge seal begins to degrade. Units with warm-edge spacer technology — which we use as standard — have longer seal life than older aluminium spacer designs. Proper fitting is also important: a poorly fitted unit that allows water ingress will fail sooner regardless of unit quality.