Project Estimator
Guttering Calculator
Calculate the right guttering system and components for your property. Enter your roof dimensions, and we'll recommend the correct gutter profile, calculate every bracket, union, outlet, and downpipe you need, then let you add it all to your basket.
☔ How It Works
- 1 Enter your roof area, pitch, and gutter run length — we calculate the flow rate and recommend the right system
- 2 Choose your guttering system and colour — or accept our recommendation
- 3 Review your full material list, adjust quantities, and add everything to your basket
Based on BS EN 12056-3:2000
Calculations assume a rainfall intensity of 75mm/hr (0.021 L/s/m²). For complex roof geometries, verify with a structural engineer.
Calculations assume a rainfall intensity of 75mm/hr (0.021 L/s/m²). For complex roof geometries, verify with a structural engineer.
Prices shown exclude VAT. All quantities include your chosen waste allowance.
Your Guttering Project
Rainwater system estimator
Effective Roof Area
The area of roof draining into this gutter run. Enter total m² or use length × width.
Roof Area (m²)
Roof Length (m)
Along the eaves — this is your gutter run
Roof Depth (m)
From eaves to ridge (or to the wall)
Roof area: 60 m² • Gutter run: 10 m
Gutter Run Length (m)
The length along the eaves where the gutter sits
Roof Pitch
Number of Downpipes
Increase to reduce load per outlet
Building Height
Flow Load Per Outlet
1.26
L/s
Total Runoff
1.26
L/s
112mm Half Round guttering is suitable for this flow rate.
Waste Allowance
Your Measurements
Choose Guttering System
Our recommendation is highlighted. You can override it.
Choose Your Colour
Loading colours...
Matched Components
Your Material List
System: Half Round
Run: 12m
Waste: 10%
VAT (20%)
£0.00
🛒 Add All to Basket
All items added to your basket!