Stormwater Runoff Volume Estimator
Estimate event runoff volume across multiple surfaces with editable coefficients and capture share.
What would you like to do next?
Keep every surface contribution visible in an event total
List roof, paving, gravel, landscape or other surfaces with area and a runoff coefficient from zero to one. Enter rainfall depth and modeled capture share. The estimator converts millimetres over square metres to cubic metres, applies each coefficient and reports individual plus combined runoff volume.
Move from event volume to a verified drainage model
A single depth calculation does not represent intensity, duration, time of concentration, infiltration timing, routing, storage, blockage or overflow. Coefficients depend on local conditions and method. Apply approved design storms, survey levels, climate allowances, regulatory criteria and professional drainage review.
Frequently asked questions
What coefficient range is accepted?
Values are limited from zero to one.
Is rainfall intensity used?
No. This screen calculates event volume from total depth.
Does this size a drain?
No. Drainage sizing requires flow, routing and design criteria.