Runoff volume--
Gutter Drainage Calculator
Estimate roof runoff from roof area and rainfall.
Updated May 2026No signup requiredBuilt for mobile
Why people use this
Use this calculator for a fast field estimate before buying parts, loading gear, planning work, or making a practical project decision.
FAQ
Gutter Drainage Calculator questions
Is this estimate exact?
No. Use it as a planning estimate and verify important numbers with equipment ratings, product labels, local rules, and real-world conditions.
Should I add a safety margin?
Yes when weight, fuel, power, towing, livestock, weather, or safety are involved. A margin helps cover real-world variation.