Rainfall Rate Calculator
Convert rainfall depth and duration into an average rate and theoretical area volume.
What would you like to do next?
Divide measured depth by elapsed time
Choose metric or Imperial measurements, then enter total rainfall depth, hours, minutes and an optional catchment area. The calculator reports average depth per hour in both unit systems and multiplies depth by area to show the theoretical liters and US gallons that fell across the surface. No runoff factor is applied, keeping the geometric volume separate from collection efficiency.
An event average can hide short peaks
A gauge total divided by event duration does not reveal the highest five-minute or hourly intensity. Wind, gauge exposure, spatial variation, roof losses, first flush, overflow and drainage all affect measured or captured water. The tool does not classify severity, flood risk or design drainage capacity; obtain local observed and design data for those decisions.
Frequently asked questions
How is average rainfall rate calculated?
Total depth is divided by the complete duration entered.
Is runoff efficiency included?
No. Area volume is the theoretical depth times area before losses.
Does the average show peak intensity?
No. Short intervals can be much more intense than the event average.