Whole-yard planning logic
Runoff gallons = drainage area x rainfall inches x 0.623 x runoff factor. Storage area = runoff cubic feet divided by temporary ponding depth.
RainYard Tools
Whole-yard screen
Yard Drainage Calculator
Estimate runoff, temporary storage, and surface area needed when a yard stays wet after rain.
Runoff to manage567 galSelected storm volume for the drained area.
Storage target75.8 cu ftTemporary storage before overflow.
Surface area227 sq ftIf water spreads at the chosen ponding depth.
Example
A 1,400 sq ft yard section, 1 inch of rain, and a 65% runoff factor create about 567 gallons. If you can safely pond 4 inches, that is about 227 sq ft of temporary storage area.
Use this before choosing the fix
A wet yard can need regrading, better downspout routing, a swale, a shallow basin, or a French drain. This page helps you see the water volume before you pick the hardware.
The surface area result is a screening number
It does not prove the basin will infiltrate fast enough. Slow soils, high groundwater, and a blocked outlet can still leave the yard wet.
Questions
Common checks.
Is this the same as a French drain calculator?
No. This page starts with the yard volume problem. A French drain page compares that water with trench storage and discharge.
What runoff factor should I use for lawn?
Many lawns screen in the 30-70% range depending on slope, compaction, and saturation. Packed or bare areas run higher.
Should I use a deeper ponding depth to shrink the area?
Only if that water can sit safely away from the house, walks, and play areas.
Helpful referencesEPA green infrastructure typesEPA National Stormwater Calculator