How long should I water my lawn?
Enter your lawn, the water it needs and your sprinklers, get the minutes and the gallons.
The weekly amount is yours to set: 1 inch is only an example. Virginia Cooperative Extension’s rule of thumb is about 1 inch a week, rain included; other services give other numbers — see the questions below.
Set straight-sided cans across one zone, run it for a timed run, and average the water depths.
Rate = 96.25 × gpm ÷ area in ft²: a gallon is 231 in³ and a square foot is 144 in². Enter one zone’s flow and its own area.
Use the price on your own bill; a bill in CCF (748 gallons) divides by 0.748.
How much water does a lawn need per week?
There is no single figure, so the calculator asks for yours. Virginia Cooperative Extension gives a rule of thumb: most turfgrasses need about 1 inch of water per week, from rain or irrigation together, to keep growing in warm weather, and says it varies with the grass, the climate and the soil. Colorado State University Extension’s schedule for cool-season lawns in Colorado is 0.75 inch a week in late April, 1 inch in May and June, 1.5 inches in July and August, 1 inch in September and 0.75 inch in early October, rain included. University of Minnesota Extension advises watering infrequently — once a week or less — and notes that, depending on the soil, a lawn may need as little as half an inch.
How many gallons is an inch of water on a lawn?
One inch of water over one square foot is 144 cubic inches, and a US gallon is 231 cubic inches, so it is 144 ÷ 231 = 0.623 gallons. A 1,000 ft² lawn watered 1 inch takes 623 gallons. In metric it is simpler: 1 millimeter over 1 square meter is exactly 1 liter. The rainwater harvesting calculator uses the same constant.
How long should I run my sprinklers?
Divide the water you want to apply by your sprinkler’s precipitation rate, then multiply by 60. To measure the rate, set straight-sided cans across a zone, run the sprinklers for a timed run and average the depths: 0.25 inch in 15 minutes is 0.25 × 60 ÷ 15 = 1 inch per hour, so 1 inch takes 60 minutes. Or work from the flow: 1 gpm for an hour is 60 × 231 cubic inches spread over 144 square inches per square foot, which is 96.25 inches per hour per gpm per square foot, so a zone of 10 gpm over 1,000 ft² applies 96.25 × 10 ÷ 1,000 = 0.96 inch per hour.
How do I stop water running off the lawn?
Cut each watering into shorter runs with soak-in time between. Colorado State University Extension’s Table 4 gives the number of cycles: pop-up spray heads run 0–16 minutes in one cycle, 16–24 minutes in two and over 24 minutes in three; rotors run 0–48 minutes in one, 48–72 in two and over 72 in three. A 26-minute spray watering becomes three runs of 9 minutes. Virginia Cooperative Extension’s approach is to watch for puddles: in its example, 60 minutes deliver an inch but water pools at about 30 minutes, so the sprinklers run no longer than 30 minutes at a time and the lawn is watered twice a week.
How much does it cost to water a lawn?
Multiply the gallons by your water price. If your bill is in CCF (100 cubic feet = 748 gallons), divide the CCF price by 0.748 to get a price per 1,000 gallons. For example only, at $5.00 per 1,000 gallons the 623 gallons of one inch on 1,000 ft² cost $3.12 a week, or $13.51 for a month of weekly watering. Use the price on your own bill.
Sources: Virginia Cooperative Extension, publication 430-010, “Summer Lawn Management: Watering the Lawn” (Virginia Tech, last reviewed June 2024); Colorado State University Extension, CMG GardenNotes #265, “Methods to Schedule Home Lawn Irrigation” (reviewed April 2023); University of Minnesota Extension, “Water-saving strategies for home lawns” (reviewed 2022). A US gallon is 231 cubic inches (NIST Handbook 44). Water from the roof instead? Use the rainwater harvesting calculator. Planting a lawn: sod calculator, grass seed calculator; feeding it: fertilizer calculator. How we check our calculators.