RAIN GARDEN CALCULATOR

Fill out our Rain Garden Calculator to estimate how much stormwater your rain garden can capture, redirect, filter, and help clean before it reaches local waterways.

Rain Garden Size Calculator (Lake Simcoe Watershed)
Lake Simcoe Watershed

Rain Garden Size Calculator (sq ft)

Use this form to estimate a recommended rain garden area to help slow stormwater and reduce runoff to local waterways. Results are an approximation for planning purposes.

Roof, driveway, or yard area that drains toward the rain garden.
Higher values produce more runoff.
Default is 1.0" as a simple planning baseline.
Slower soils generally need a larger rain garden.
Rain gardens temporarily hold water before soaking in.
Rain gardens should typically drain within 24–48 hours.

Estimated Results

Note: Final design should consider grading, setbacks from foundations, utilities, and real soil conditions.