How to use the rainfall runoff volume calculator
Compute runoff from rainfall over a catchment. Enter catchment area, rainfall, runoff coefficient in the fields above; the runoff volume are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “stormwater”, “roof rain collection”, “rainwater harvesting”, “calculate rainfall runoff volume”, “find runoff volume”.
Formula
Variables
- A — Catchment area (m²)
- r — Rainfall (mm)
- c — Runoff coefficient
Worked example
With catchment area = 100 m², rainfall = 25 mm, runoff coefficient = 0.9, the calculator gives runoff volume ≈ 2,250 L; runoff volume ≈ 2.25 m³.
Frequently asked questions
What is the rainfall runoff volume calculator used for?
Compute runoff from rainfall over a catchment. It helps with questions such as “stormwater”, “roof rain collection”, “rainwater harvesting”.
What is the formula for the rainfall runoff volume calculation?
Runoff volume (L) = A × r × c. Runoff volume (m³) = [Runoff volume] / 1000. Here A is catchment area (m²), r is rainfall (mm), c is runoff coefficient.
What inputs do I need for the rainfall runoff volume calculator?
You need catchment area in m², rainfall in mm, runoff coefficient. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the rainfall runoff volume calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the rainfall runoff volume result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.