Spouting & Guttering Calculator NZ 2026

This calculator works out how much spouting you need, along with the number of downpipes and brackets, so you can price a re-gutter or a new build in New Zealand without guesswork. Spouting, the New Zealand term for roof gutters, runs along the eaves to catch rain and carry it to downpipes, and getting the quantities right matters for both the materials order and the system's performance. Too few downpipes and the gutters overflow in heavy rain, which is common in our climate; too many and you waste money and pierce the gutter more than needed. As a rule of thumb, a downpipe is provided for roughly every 10 to 12 metres of gutter, and more where a large roof area drains to one run, while brackets to hold the spouting are spaced around every 600mm or to the manufacturer's specification. You enter the total length of roof edge that needs guttering, which you can measure off the eaves or estimate from the building's perimeter, and the spacing you want for downpipes, and the calculator returns the total spouting length, the number of downpipes, and the number of brackets. This gives you a clean materials list to take to the supplier and a basis to check a quote. For an accurate order, measure each run of eaves rather than relying on the floor plan, allow extra length for corners and joins, and remember that internal and external corners, stop ends and downpipe droppers are additional fittings. Always size downpipes and gutters for your roof catchment and rainfall; this is a quantities estimate, not a stormwater design.

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36 m
spouting length needed
Downpipes3
Brackets60
Joiners (per 4m)9

Add extra for corners and joins. Downpipes and gutters must suit your roof catchment and rainfall. A quantities estimate only.

How it works

The spouting length equals the length of roof edge you enter. The number of downpipes is that length divided by your downpipe spacing, rounded up. Brackets are spaced about every 600mm, so the length divided by 0.6, rounded up. Joiners assume spouting comes in roughly 4 metre lengths.

Worked example

A house with 36 metres of eaves to be guttered needs 36 metres of spouting. With a downpipe every 12 metres, that is 3 downpipes. At a bracket every 600mm, 36 divided by 0.6 is 60 brackets. Allowing for spouting in 4 metre lengths, you would have about 9 joins, plus corner and stop-end fittings to add separately.

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Frequently asked questions

How many downpipes do I need?

As a guide, provide a downpipe for roughly every 10 to 12 metres of gutter, and more where a large roof area drains into one run. Under-providing downpipes causes overflow in heavy rain, so size them to your roof catchment and local rainfall.

How far apart should gutter brackets be?

Spouting brackets are typically spaced around every 600mm, or to the manufacturer's specification, with closer spacing in areas of heavy rain or snow. This calculator uses 600mm centres to estimate the bracket count.

What fittings do I need besides spouting?

Besides the gutter lengths, downpipes and brackets, you need internal and external corners, stop ends, joiners, and downpipe outlets or droppers. Measure each run and corner, and add these fittings to the order separately.