Gutter Slope Calculator
Enter your run and pitch to find the vertical drop you need to build in.
High-center splits one long gutter into two shorter runs that drain to a downspout at each end.
A gutter slope calculator finds the drop, run, or pitch a rain gutter needs to drain to its downspout. The tool solves one slope relationship — Drop = Run × Pitch — three ways, and converts between feet, inches, millimeters, centimeters, and percent. Use it to plan a new install, size the fall for long runs, or check an existing slope. The main parts are the input fields for run, drop, and pitch, the unit selectors, the live diagram, and the result panel with grade percentage.
What is Gutter Slope?
Gutter slope is the downward tilt of a gutter from its high end to the downspout, measured as vertical drop over horizontal run. Slope is also called pitch or fall. The minimum standard slope is 1/4 in per 10 ft (0.025 in/ft, 0.21% grade). Slope moves rainwater along the channel to the downspout instead of letting it pond against the fascia and roofline. Drag the run and pitch below to see the drop change against the level reference.
Slope = drop ÷ run. Drag run and pitch to watch the vertical drop change against the level reference.
Gutter Slope Formula
The gutter slope formula is Drop = Run × Pitch. The same slope relationship rearranges two more ways: Pitch = Drop ÷ Run, and Run = Drop ÷ Pitch.
- Drop is the vertical height difference between the high end and the downspout end, in inches.
- Run is the horizontal length of the gutter to the downspout, in feet.
- Pitch is the slope expressed as inches of fall per foot of run (in/ft).
All inputs convert to inches and feet internally, then convert back to your chosen units. Grade percentage is computed as (pitch ÷ 12) × 100.
Typical Pitch Values and Drop Reference
Most gutter installs target a slope between 1/4 in per 10 ft and 1/16 in per ft. Use these tables to sanity-check your result.
| Pitch | In/ft | Grade | mm / m | Use |
|---|---|---|---|---|
| 1/4 in per 10 ft | 0.025 | 0.21% | 2.1 mm/m | Minimum standard slope |
| 1/2 in per 10 ft | 0.05 | 0.42% | 4.2 mm/m | Heavy rainfall regions |
| 1/16 in per ft | 0.0625 | 0.52% | 5.2 mm/m | Common residential pitch |
| 1/8 in per ft | 0.125 | 1.04% | 10.4 mm/m | Steep, fast-draining |
| Run length | Drop (in) |
|---|
Why Gutter Slope Matters
Gutter slope matters because it controls whether rainwater drains or pools. There are 3 outcomes by slope: too shallow ponds water against the fascia, ideal drains cleanly to the downspout, and too steep drains fast but tilts visibly next to the roofline. Select an outcome to see the effect.
How to Calculate Gutter Slope
To calculate gutter slope, divide the vertical drop by the run length: Pitch = Drop ÷ Run. For a new install, multiply the run by the pitch to get the drop. A 32 ft gutter draining to one downspout at 1/4 in per 10 ft needs a drop of 32 × 0.025 = 0.80 in. Mark the high end about 13/16 in above the downspout end.
Measure the run
Measure the horizontal length from the high end of the gutter to the downspout, in feet.
Choose a pitch
Use 1/4 in per 10 ft as the minimum standard slope. Go to 1/16 in per ft for common residential pitch.
Multiply for the drop
Multiply the run by the pitch to get the drop in inches, then mark the downspout end that much lower.
Gutter Slope Rate
The gutter slope rate is the fall per unit of run, written as inches per foot or inches per 10 feet. The minimum rate is 1/4 in per 10 ft (0.025 in/ft). Heavy rainfall regions use 1/2 in per 10 ft (0.05 in/ft, 0.42% grade). Set a pitch to read the rate in every unit.
Gutter Slope Code
Gutter slope code sets a minimum standard slope of 1/4 in per 10 ft (0.025 in/ft, 0.21% grade). Slope below that minimum lets water pond. Enter a measured slope to check it against the minimum.
Gutter Slope Per Foot
Gutter slope per foot is the vertical drop for every 1 foot of run. The common residential pitch is 1/16 in per ft (0.0625 in/ft, 0.52% grade). A 1/8 in per ft pitch (0.125 in/ft, 1.04% grade) is steep and fast-draining. Drag the slider to read the per-foot drop.
Gutter Slope Percentage
Gutter slope percentage is the grade, found with (pitch ÷ 12) × 100. A 1/4 in per 10 ft slope equals 0.21%, a 1/2 in per 10 ft slope equals 0.42%, and a 1/16 in per ft slope equals 0.52%. Set a pitch to read the grade percentage.
The complete gutter tool suite
Every gutter question has its own purpose-built calculator — fall, slope, pitch, angle, flow and outlet spread, for the US, UK, Australia and New Zealand.