Gutter Slope Calculator Open Calculator
UK · metric

Gutter Slope Calculator UK

A metric-first gutter slope planner for UK rainwater systems — work in millimetres per metre and 1:X ratios, with in/ft and degrees alongside.

UK gutter slope checker
Live

Enter the run and the height drop between the high end and the outlet — the slope appears below.

Live preview — the gutter tilts to your slope
level reference drop run HIGH END LOW END →
Gutter (sloped) Water flow Level reference
Enter a run and a drop — the slope appears here.
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The UK gutter slope calculator turns a measurement into a slope: enter the run in metres and the height drop in millimetres between the high end and the outlet, and it reports the slope as a 1:X ratio, mm per metre, a grade percentage and an angle, then flags whether it looks too shallow. It is the companion to the UK fall calculator, which goes the other way — from a chosen fall rate to the drop to build in.

On the job

Setting a UK gutter slope

Interactive — set a UK gutter slope
run drop water runs to the outlet
Treat these as guidance figures and confirm against BS EN 12056-3, Building Regulations Part H and the manufacturer's instructions for your specific gutter and rainfall.
Frequently asked

Questions answered

What slope should a UK gutter have?
A gentle continuous slope of roughly 1:350 to 1:600 — about 1.7 to 3 mm per metre — toward the outlet suits most UK eaves gutters. The exact figure depends on run length, rainfall and the gutter profile.
Is gutter slope the same as gutter fall in the UK?
Yes. In British usage "fall" and "slope" both mean the gentle downward gradient toward the outlet. This page uses "slope" and quotes it as mm per metre and a 1:X ratio; the figures are identical to the fall calculator.
How do I check the slope of an existing UK gutter?
Measure the run in metres and the height drop in millimetres between the high end and the outlet, then enter both in Check mode. The tool returns the slope as a ratio, mm/m, percentage and angle and flags whether it looks too shallow.
What slope stops a gutter ponding?
Any consistent slope toward the outlet helps; ponding usually appears when a gutter is fitted dead level or sags between brackets. A 1:500 or steeper slope, with brackets at proper centres, keeps the channel draining.
How do I convert a UK gutter slope to inches per foot?
The calculator shows it automatically. As a guide, 1:350 is about 0.034 in/ft and 1:200 is about 0.06 in/ft. Every result lists inches per foot alongside the metric forms.

Need the full gutter slope toolkit?

Switch between drop, slope check, max run and downspout planning on the main calculator — with the same live diagram.

Open the main calculator