About this tool
Sprinkler & Drip Run-Time Calculator is a free, in-browser tool that tells you how long to run irrigation to deliver a target amount of water. Choose sprinkler or drip mode, enter the target water depth in inches, and it returns the run time in minutes plus a supporting figure. Nothing is uploaded; the math runs on your device.
In sprinkler mode you either enter the precipitation rate directly (inches per hour) or compute it from flow and area, where rate = 96.25 × GPM ÷ area in square feet; then run time in minutes = (target depth ÷ rate) × 60. In drip mode the tool converts depth to gallons with gallons = target depth × 0.623 × area, then run time in minutes = gallons ÷ (emitter GPH × number of emitters) × 60. The constant 96.25 converts gallons per minute over an area into inches per hour, and 0.623 is the gallons needed to cover one square foot an inch deep.
Use the 'catch-can' method to find your sprinkler's real precipitation rate: place straight-sided cups on the lawn, run for a set time, and measure the average depth. For drip, read the emitter flow (GPH) off the fittings and count how many feed the zone.