Estimate how much water falls on an area during rainfall. Enter rainfall depth and surface area to calculate rain volume in gallons, liters, cubic feet, cubic meters, and runoff after a runoff coefficient.
Rainfall depth:
Enter how much rain fell, such as 1 inch or 25 millimeters.
Collection area:
Enter the area the rain falls on, such as a roof, yard, garden, driveway, or field.
Runoff coefficient:
Use a value between 0 and 1 to estimate how much water runs off or can be collected.
Rainfall volume:
The calculator converts depth and area into gallons, liters, cubic feet, and cubic meters.
A rainfall calculator is useful for rainwater collection, rain barrels, drainage planning, garden watering, lawn care, stormwater estimates, roofing, landscaping, agriculture, and understanding how much water falls during a storm.
Actual collected water can vary because of splash loss, evaporation, gutter layout, soil absorption, slope, surface material, and drainage conditions.
Your result shows the total rainfall volume over the selected area. The runoff result applies the runoff coefficient to estimate how much water may flow off the surface or be collectable.
Multiply rainfall depth by the collection area, then convert the volume into gallons, liters, cubic feet, or cubic meters.
One inch of rain on 1,000 square feet is about 623 gallons before runoff losses.
A runoff coefficient estimates the portion of rainfall that runs off a surface instead of soaking in, evaporating, or being lost.
Yes. Use your roof collection area, rainfall depth, and a runoff coefficient to estimate how much water could be collected.