RainYard Tools
Roof flow
Gutter Flow Calculator
Estimate gallons per minute coming from a roof during a rainfall intensity.
Before you calculate
Use it to sanity-check whether a roof section overwhelms a gutter or downspout.
- Intensity is different from total storm depth.
- Leaves and screens reduce real capacity.
- Overflow should not dump beside the foundation.
Peak flow22.2 gpmEstimated flow from the roof section.
Per minute22.2 galWater arriving each minute.
Per hour1,333 galIf intensity holds for an hour.
1
Use the roof section served by one gutter run.
2
Enter a rainfall intensity.
3
Compare flow with your downspout plan.