Polycarbonate Roof Calculator
Enter your roof size and we’ll recommend the best sheet setup, calculate the full kit, and show a quote you can add to basket.
We’ll calculate how many sheets you need plus glazing bars, trims, fixings, and sealing tape kits (breather and foil tape). For attached roofs we’ll also include wall flashing tape. You’ll see your quote like a basket with product images, an estimated total, and an estimated delivery window (–5 working days).
Enter your roof measurements
Choose your roof type and enter the width and projection. These measurements help us calculate your sheets, glazing bars and accessories.
View measurement guide
View measurement guide
Sheet options
Your quote
Your roof layout will appear here once we calculate your quote.
Your kit will appear here once we calculate it.
Polycarbonate Roof Sheet Calculator
Planning a new pergola, carport, lean-to or garden canopy?
Use this simple polycarbonate roof sheet calculator to work out how many multiwall polycarbonate sheets you need, along with the right accessories to finish the job properly.
Once you’ve got your result, you can add the sheets straight to your basket from our Multiwall Polycarbonate Sheets range and get them delivered in 3–5 working days.
How the Polycarbonate Roof Calculator Works
Our calculator is designed around the way multiwall polycarbonate is normally installed in the UK:
- Sheets usually run down the slope of the roof
- Sheet length = the length of your roof
- Number of sheets = roof width ÷ sheet width
You only need three measurements:
- Total roof width (mm)
- Total roof length (mm)
- Your chosen sheet width and thickness
The calculator then works out:
- How many sheets you need
- An example layout
- Recommended accessories
Enter Your Roof Measurements
You’ll need:
- A tape measure
- The planned external size of your structure
- Your preferred sheet thickness (10mm, 16mm or 25mm)
👉 Tip: It’s usually easiest to measure in millimetres (mm).
Example Calculations
Example 1 – Small Pergola
- Roof width: 3100mm
- Roof length: 3000mm
- Sheet width: 1050mm (16mm Corotherm)
3100 ÷ 1050 = 2.95 → 3 sheets needed
You would order:
- 3 × 16mm sheets, 1050mm wide, 3000mm long
- 2 × glazing bars
- 3 × end closures
- Breather tape, foil tape and fixing buttons
Example 2 – Larger Carport
- Roof width: 4200mm
- Roof length: 4000mm
- Sheet width: 1050mm (25mm Corotherm)
4200 ÷ 1050 = 4 sheets needed
You would order:
- 4 × 25mm sheets, 1050mm wide, 4000mm long
- 3 × glazing bars
- 4 × end closures
- Breather tape, foil tape, fixing buttons and flashing tape
Which Polycarbonate Thickness Should I Choose?
As a quick guide:
- 10mm – Light-duty canopies, smaller lean-tos, budget projects
- 16mm – Most pergolas, garden covers and open structures
- 25mm – Enclosed rooms, garden offices, higher insulation
For a pergola or standard garden canopy, 16mm multiwall polycarbonate is normally the best balance of strength, light and cost.
Accessories You’ll Usually Need
For most roofs you’ll also need:
- Glazing bars – to join and support the sheets
- Breather tape – for the bottom edges of sheets
- Aluminium foil tape – for the top edges
- End closures – to seal and protect the sheet ends
- Fixing buttons – to secure sheets to rafters
- Wall flashing tape – where the roof meets a wall
If you’re unsure, contact us and we’ll help you build a complete list for your project.
Need Help with Your Roof Design?
If you’re not confident with measurements or you have an unusual roof shape, we’re happy to help.
- Call us on 01295 231617
- Email sales@polycarbonatex.co.uk
- Or use our Polycarbonate Roof FAQs for more guidance
We’ll help you choose the right sheet thickness, colour and layout for your project.