Guttering Length Calculator

How it is calculated

All lengths are in metres. The engine rounds up to whole gutter lengths because they are sold as fixed pieces.

pieces = ceil(roof_edge ÷ piece_length)
unions = pieces − 1
brackets = floor(roof_edge ÷ bracket_spacing) + 1
downpipes = max(1, ceil(roof_edge ÷ 10))
downpipe run = downpipes × downpipe_height

The "+ 1" puts a bracket at both ends of the run. Only the roof edge is required. If piece length, bracket spacing or downpipe height is left blank, the tool uses 3 m, 1 m and 3 m; but a value you actually type that is zero or negative gives no result rather than being replaced. Very large entries (roof edge above 10,000 m, or any other field above 1,000 m) are also rejected. The rule of one downpipe per 10 m of gutter is built in. Gutter length shown is the pieces total, so it can exceed the roof edge.

Common mistakes

• Entering the roof edge in feet. The fields are in metres, so a 40 ft run (about 12.2 m) typed as 40 more than triples the order.
• Entering the bracket spacing in centimetres (60) instead of metres (0.6); the bracket count then collapses to 2.
• Adding up each separate roof edge and treating them as one run. Each run has its own end brackets and unions, so work out long straight runs and short ones separately.
• Assuming the downpipe count follows your outlets. The tool simply allows one per 10 m, so use your own count if the design has more outlets.
• Leaving the piece length blank and forgetting that 3 m is then assumed: with a 12 m edge that gives 4 pieces and 3 unions, wrong if your gutters come in 4 m lengths.