Guttering Calculator
Sections, unions, brackets, angles, stop ends, downpipes and clips - all in one place
Standard uPVC: 2 m or 4 m - Cast iron: 1.83 m
600 mm recommended for uPVC
Guttering Runs
Eaves to ground or drainage point
Standard: 2 m or 2.5 m
Every 1200 mm maximum for uPVC - 900 mm cast iron
Typically 2 (swan-neck offset at top)
5% is usually enough - guttering has minimal waste if measured carefully
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Results
Guttering
Total Gutter Length
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linear metres
Sections to Order
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sections
Fascia Brackets
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brackets
Fittings
Unions / Connectors
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between sections
Angles / Corners
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total (all runs)
Stop Ends
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total (all runs)
Outlets
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running outlets
Run Breakdown
| Run | Length | Sections | Unions | Brackets | Angles | Stop Ends | Outlets |
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Frequently Asked Questions
How much guttering do I need?
Measure each eaves run length. Standard uPVC guttering comes in 2 m or 4 m lengths - divide run by length and round up. Add: one stop end per run end, one outlet per run (max 12 m per outlet for 112 mm half-round), unions to join lengths, and angle pieces for corners. One downpipe per outlet.
What size guttering do I need?
Most standard UK houses use 112 mm half-round or 114 mm square guttering - suitable for pitches up to 35° and runs up to 12 m per outlet. For larger roofs, steep pitches (over 45°) or high-rainfall areas: 150 mm guttering and 68-75 mm downpipes. Per Approved Document H: the system must handle 75 mm/hour rainfall intensity.
What fall is needed for guttering?
Minimum gradient of 1:600 (approximately 1.7 mm per metre). In practice many installers use 1:400 for reliable drainage and to allow for minor inaccuracies. For a 6 m run at 1:600, the outlet end is approximately 10 mm lower than the closed end.
What is the difference between half-round and square guttering?
Half-round: traditional curved profile, most common on older UK properties. Square: flat back and base, popular on modern properties. Ogee: decorative S-shaped front, used to match period-style properties. Both 112 mm profiles carry similar flow capacity - flow depends on cross-sectional area and outlet size, not just profile.
How often should guttering clips be fixed?
Maximum 600 mm centres for uPVC gutter brackets. Fix a bracket within 150 mm of each side of union pieces and expansion joints. In heavy snow loading areas, reduce to 450 mm centres. Use stainless steel or galvanised fixings. Brackets needed = (run length ÷ 0.6) + 1.
What Building Regulations apply to guttering and drainage?
Covered by Approved Document H. System must handle 75 mm/hour rainfall intensity for most of the UK. Rainwater must discharge to a surface water drain, soakaway or watercourse - not to a foul drain unless no other option exists and the local authority permits it. Building Regulations approval required for extensions and new dwellings.