Gutter Slope Calculator Open Calculator
Angle to drop

Gutter Angle Calculator

Start from a fall angle in degrees and get the slope and drop you can actually mark out — inches per foot, millimetres per metre, percent and ratio.

Angle → slope & drop
Live

Enter a fall angle and the run — get the drop to mark plus the slope per foot and metre.

Fall angle below level (exaggerated)
level reference (0°) —
Gutter Level
Slope & drop for this angle
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Drop over the run
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Inches per foot
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mm per metre
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Ratio
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The gutter angle calculator works the angle both ways. Leave the unit on degrees to enter a fall angle and read the equivalent slope and drop, or switch the unit to a ratio, percentage or inches-per-foot to convert the other direction. Because the maths is rise ÷ run = tan(angle), every form stays perfectly in step, and the preview tilts so a sub-degree slope is visible at a glance.

From angle to wall

Turn degrees into a mark

Interactive — from angle to a marked drop
run drop water runs to the outlet

If you already know the slope and just want the degrees, the gutter slope angle page is set up for that direction. For full run, drop and outlet planning, open the main calculator.

Frequently asked

Questions answered

How do I calculate a gutter angle?
Set the angle in degrees and the calculator returns the matching slope as inches per foot, millimetres per metre, a percentage and a 1:X ratio. The relationship is rise ÷ run = tan(angle), so a 0.5° gutter has a slope of tan(0.5°) ≈ 0.0087, or about 0.10 in/ft.
What angle is a 1 in 100 gutter fall?
A 1:100 fall is 1 unit of drop for every 100 of run. Its angle is arctan(1 ÷ 100) ≈ 0.57°. Type 100 with the ratio unit, or 0.57 in degrees, to see every equivalent.
How many degrees is a quarter inch per foot?
A 1/4 inch per foot slope is a rise-over-run of 0.25 ÷ 12 ≈ 0.0208, and arctan of that is about 1.19°. That is on the steep side for a gutter.
Should I set my gutter by angle or by drop?
Drop is easier on site, because a fraction of a degree is hard to read on a spirit level. Use this tool to convert your target angle into a drop per foot or per metre, then mark that vertical distance along the run.
What angle finder do I need for gutters?
A digital angle gauge or a phone inclinometer can read tenths of a degree, which is enough for gutter work. Set it on the gutter top edge once hung and compare against the angle this calculator gives for your chosen slope.

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