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Gutter Bracket Calculator — Brackets, Fittings & Guttering
Calculate gutter brackets, fittings and guttering lengths for your roof. Includes outlets, corners and union joints.
Total length of all gutter runs
One per downpipe
Internal and external corners
FloPlast PVC-U max 1000mm (Half Round/Square), 800mm Ogee; reduce to 400mm in heavy-snow areas. 600mm is a conservative default.
Default: 4m standard lengths
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How We Calculate This
This calculator divides the total gutter run by the bracket spacing to find the run-spacing brackets, then adds an extra support bracket within 150mm of every corner, outlet, union joint and stop end — as required by the FloPlast PVC-U Rainwater and GMT installation guides. It also divides the run by the gutter length to find how many lengths and union joints you need.
The formula
Spacing brackets = ceil(Total run ÷ Spacing) + 1
Fitting brackets = corners + outlets + union joints + stop ends (one within 150mm of each)
Total brackets = Spacing brackets + Fitting brackets
Gutter lengths = ceil(Total run ÷ Length per piece)
Union joints = Gutter lengths − 1
Stop ends are assumed to be 2 for a single straight run. A continuous wrap-around run that returns on itself via corners may have fewer free ends — adjust the count if your layout differs. Standard PVC-U gutter is supplied in 4m lengths (FloPlast, BS EN 607).
Frequently Asked Questions
FloPlast's PVC-U installation guide allows up to 1000mm (1m) centres for Half Round and Square gutter, 800mm for Niagara Ogee, reducing to 400mm in heavy-snowfall areas. Cast iron and aluminium are typically 900mm–1m. 600mm is a sensible conservative default for exposed locations. Whatever the run spacing, an extra bracket must be fitted within 150mm of every joint, union, corner and stop end so the gutter does not sag at the fittings.
Typically one outlet per downpipe. Most houses need 2-4 downpipes depending on roof area. A single downpipe can serve up to about 50m² of roof area. Use our Gutter Sizing Calculator to determine the correct gutter and downpipe sizes for your roof.
You need brackets, outlets (for downpipes), union joints (to connect gutter lengths), corners (internal/external), and stop ends. This calculator works out all the fittings.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.