CalculatorCritical
Rainfall Runoff Calculator
For consumers, students & professionals. Result, assumptions, chart, comparisons and recommendations.
Unit system— all inputs and outputs convert automatically
Inputs
Enter your data — results update live.
Runoff volume
2,250
L per event
Notes
- • Formula: Rational Method — Q = C·i·A · f(soil,moisture).
- • Peak flow within typical residential capacity.
- • Impervious surface — consider a rain garden or cistern.
Breakdown chart
Visual comparison of each component ().
- Effective runoff coefficient
- 0.90
- Runoff depth
- 22.50 mm
- Volume in m³
- 2.25 m³
- US gallons
- 594.00 gal
- Peak flow rate
- 0.63 L/s
- Harvestable volume (90%)
- 2025.00 L
Methodology & sources
Formula
Runoff (L) = area × rainfall × C · f(soil) · f(moisture); Peak flow = volume / durationSources
- • USGS
- • US EPA Stormwater BMP Handbook
- • NRCS TR-55 Runoff Curve Numbers