Building tool
Gutter Size Calculator
Estimate adjusted roof drainage area, runoff flow, gutter size, and downspout count.
Runs in your browserResult
- Adjusted roof area
- 1,980 sq ft
- Peak runoff
- 82.3 gal/min
- Starting gutter size
- 5-inch K-style
- Downspouts
- 4
- Area per downspout
- 495 sq ft
Valleys, roof geometry, outlet location, local design rainfall, gutter profile, slope, and debris can require larger components.
How to use this gutter size calculator
- Measure the project, enter the dimensions in the units shown, and add the waste, spacing, coverage, or material settings that apply.
- Review the calculated totals, units, and assumptions. Check the inputs and units before relying on the result.
- Change one input at a time to compare another case, then copy or save the result you plan to use.
About this gutter size calculator
Use the Gutter Size Calculator to estimate adjusted roof drainage area, runoff flow, gutter size, and downspout count. The result changes when you adjust the values or options above.
You can also use it to compare results after changing one input.
Example
Enter roof drainage area, pitch, and rainfall intensity to estimate runoff, gutter size, and downspout count.
Common uses
- → estimate adjusted roof drainage area, runoff flow, gutter size, and downspout count
- → compare results after changing one input
- → save an estimate for planning or comparison