How Much to Water Your Lawn: Inches, Minutes, Gallons

The weekly number, source by source

This guide is about established lawns: grass that has rooted in and is mowed regularly. Seeding a new or thin lawn is a different job, covered in how much grass seed you need.

Lawn water is measured as a depth, in inches, the same way rain is. An inch of water is the amount that would stand one inch deep if none of it soaked in or ran off. A depth works for any lawn size, which is why every source below uses it. Here is what each one says for an established lawn.

So the one inch is a starting point, not a rule. The Midwest sources put the top of the range at an inch and a half in summer heat. Florida's extension service does not count inches per week at all. It waters a fixed amount when the grass asks for it and lets the season set the spacing. For a local figure, EPA WaterSense points to your Cooperative Extension Service or your water utility.

Count the rain first

The weekly inch includes rain. EPA WaterSense says so directly, and NDSU puts it as an inch "from you, rainfall or a combination of both". So the first step each week is to find out how much fell on your lawn, then water only the difference.

Measure rain where you water

Use a rain gauge, or a straight-sided can of the kind you use for the sprinkler test below. Read it after each rain, add up the week, and empty it. If your gauge or weather service gives millimeters, the length converter turns them into inches; one inch is exactly 25.4 mm.

A forecast is not a measurement. The National Weather Service defines the chance of rain as the probability of at least 0.01 inch at a point, so even a high percentage does not tell you how much will fall. What a chance of rain means explains how to read the percentage and where to find the expected amount. NDSU's advice is simply not to irrigate while it is raining or when rain is expected; then measure what actually came down.

The weekly sum

If the rain already reached the target, you water nothing that week. UF/IFAS goes further for Florida lawns: if at least 1/2 to 3/4 inch of rain fell the day before a scheduled watering, skip it, and after rain wait until the grass shows drought stress again.

Measure your sprinkler: the can test

Knowing you need 0.6 inch is only half the answer. You also need to know how fast your sprinkler puts water down, and that differs a lot from one sprinkler to the next. Every source here uses the same trick: catch the water in cans and measure it with a ruler. EPA WaterSense suggests empty tuna cans; Illinois mentions coffee cans or similar straight-sided containers; NDSU uses flat-bottomed cups.

How to run it

1. Collect straight-sided, flat-bottomed containers. Nebraska Extension uses about 10 to 15 per zone for a sprinkler system; a few for a single hose-end sprinkler is enough, as in the EPA and UF/IFAS versions.
2. Spread them across the area the sprinkler covers. UF/IFAS sets them in a straight line from the sprinkler to the edge of the pattern. NDSU spaces cups 5 to 10 feet apart along that line. Nebraska spaces cans 10 to 15 feet apart, never more than 15, across a system zone.
3. Run the water for a set time. UF/IFAS, Colorado State and Nebraska use 15 minutes. Nebraska notes some systems needed 30 minutes before the cans held a measurable amount.
4. Measure each can with a ruler and average them. Add the readings and divide by the number of cans, as Nebraska describes. If you read the ruler in fractions, how to read a tape measure turns 1/4 or 3/8 inch into a decimal.

From cans to minutes

Say six cans caught these depths after 15 minutes: 0.30, 0.20, 0.25, 0.35, 0.15, 0.25 inch. The sum is 1.50, so the average is 1.50 ÷ 6 = 0.25 inch. Scale that to an hour and divide your target by it:

This matches the UF/IFAS example: about 1/4 inch in 15 minutes means 1 inch an hour, so their 1/2 to 3/4 inch takes 30 to 45 minutes. A sprinkler that catches half as much in the same time needs twice as long.

What uneven cans tell you

In the example the driest can caught 0.15 inch and the wettest 0.35. The driest spot gets only 60 percent of the average. Nebraska Extension says uneven amounts mean uneven coverage, and UF/IFAS checks for about equal amounts in every can. Colorado State suggests looking at the can that sat in any dry patch of lawn.

EPA WaterSense offers a shortcut version: time how long the sprinkler takes to put half an inch in the cans, then water that long twice a week and adjust to how the lawn responds. NDSU does the same with a full inch.

From inches to gallons

Inches are what the grass needs; gallons are what the water bill counts. The conversion needs the area of the lawn and two exact definitions from NIST: a square foot is 144 square inches, and a US gallon is 231 cubic inches.

So one inch on 1,000 square feet is about 623 gallons. In metric it is simpler: one millimeter on one square meter is one liter, so an inch of water is 25.4 liters on every square meter. For your own lawn, measure the grass area only (leave out the house, drive and beds) with the square footage calculator, then scale the numbers below or use the volume converter for liters or cubic feet.

The cubic feet column is there because many utilities bill in units of cubic feet rather than gallons. How to read your water bill explains those units and the rate tiers, so you can turn a summer of watering into dollars.

Deep and infrequent: splitting the week

All the extension sources agree on the pattern: water thoroughly, then leave the lawn alone for a while. Iowa State recommends the weekly amount in a single application or two applications 3 or 4 days apart, and warns that frequent, light watering promotes shallow roots and lush growth that is less drought tolerant. Illinois says frequent watering promotes shallow roots and weeds such as crabgrass. EPA WaterSense adds that watering too often can drown plants or result in shallow roots. NDSU puts it as a big gulp rather than a series of sips.

Your soil decides how to split it

• Clay soil. NDSU says to irrigate only once or twice a week. Colorado State notes heavy clay absorbs only about a quarter inch of water an hour, so it suggests two 10 minute runs instead of one 20 minute run. EPA WaterSense calls this cycle and soak: short runs with breaks in between so the water soaks in. Illinois says clay and slopes may need the water in two applications.
• Sandy soil. NDSU says sandy soils cannot hold a full inch, so it splits the application into two or three waterings a week.
• Runoff anywhere. If water starts to pool or run onto the pavement, stop. EPA WaterSense warns that runoff carries fertilizer and pesticide into local waterways.

The worked week

Back to the example: a 2,500 square foot lawn, a target of 1 inch, 0.4 inch of rain in the gauge, and a sprinkler that puts down 1.0 inch an hour.

In a hot, dry week at the 1.5 inch end of the Midwest range, the same lawn and sprinkler would need 90 minutes and about 2,338 gallons.

Water the lawn, not the calendar

The weekly inch is a budget. Several sources would rather you watch the grass than the date. Colorado State says the most efficient system is to water when the lawn is dry, not on a set number of days. Iowa State calls the first signs of water stress the ideal time to water.

Signs the lawn needs water

• Color. Iowa State describes a bluish green color as the first sign in cool-season grasses such as bluegrass; UF/IFAS describes a blue-gray tint in Florida lawns.
• Footprints. Both say footprints or tire tracks that stay visible after you walk across the lawn are a sign of stress.
• Folded blades. UF/IFAS adds leaf blades folded in half lengthwise.
• Dry soil below the surface. Colorado State checks the soil about three inches down with a screwdriver or small trowel. If it is damp there, it says not to water, even when the surface looks dry. Nebraska Extension uses a screwdriver the same way.

How often changes with the season

UF/IFAS keeps the amount per watering the same all year and changes only the spacing. Its table for St. Augustinegrass with 6 inch roots, assuming no rain, gives 1 to 4 days between waterings in a Miami summer and 3 to 10 days in a Miami winter; in Pensacola the winter range stretches to 8 to 28 days. EPA WaterSense likewise says irrigation schedules should be adjusted with the seasons.

Letting the lawn go dormant

Not watering is also an option. Illinois Extension says it is perfectly acceptable not to irrigate, and that most summers cool-season lawns can withstand hot, dry weather by going dormant. Its one warning: pick one approach and do not switch back and forth between watering and dormancy.

What time of day to water

The sources mostly agree on the morning and on avoiding midday:

• Early morning. Iowa State names 5 to 9 am as the best time: the water soaks in with little lost to evaporation, and the grass dries quickly afterwards. Illinois, UF/IFAS and NDSU also recommend early in the day.
• Not midday. EPA WaterSense says the hot sun evaporates much of the water before plants can take it up. Iowa State adds that midday wind spreads water unevenly and can blow it onto driveways and streets.
• Evening and night: the sources differ. Iowa State, Illinois and UF/IFAS say evening or night watering can increase turf disease, and NDSU does not recommend evening watering. Colorado State says early morning or evening, and night for automatic systems, which it says does not cause problems unless you overdo it. If your lawn has had disease trouble, the morning is the choice every source accepts.

Nebraska Extension points out a side effect of early watering: it usually runs when nobody is watching. Run the can test once in daylight so you can see heads that spray the pavement or miss the grass.

Check your local watering rules

Your community may limit when and how often you can water outside, and those limits are local. UF/IFAS tells Florida homeowners to know the limitations in place in their community and notes they may change with the season. EPA WaterSense says to contact your local water utility to find out how much and when you should be watering.

So before you set a schedule, check your water utility's website or your bill for current rules, and look again when a drought is declared. If the allowed days do not match the 3 or 4 day spacing above, fit the same weekly amount into the days you have. The schedule in this guide never overrides a local rule.

Put it on paper

A watering plan is easier to keep when it is written down next to the rest of the yard work. The free garden planner has a yearly task calendar where you can note the sprinkler minutes from your can test, the season changes to the timer, and your utility's watering days. Its bed layout grid is also a good place to mark which parts of the lawn the sprinkler misses.

Quick checklist

1. Start from about 1 inch a week, or what your local extension service gives for your area.
2. Measure the rain with a gauge or a can and subtract it.
3. Run the can test once and work out your sprinkler's inches per hour.
4. Turn the remaining inches into minutes, and split them into one or two deep waterings (more on sand, shorter cycles on clay).
5. Water early in the morning, not at midday.
6. Watch the grass and the soil, and change the spacing with the seasons.
7. Follow your utility's watering rules.

Frequently asked questions

Sources

• EPA WaterSense, Watering tips: one inch a week including rainfall, the tuna can test, midday, pooling and cycle-and-soak
• University of Illinois Extension, Watering Your Lawn: 1 to 1.5 inches a week, dormancy, cans, time of day
• Iowa State University Extension, Yard and Garden: How and when should my lawn be watered?
• NDSU Extension, The Right Way to Water Your Lawn: about 1 inch a week from irrigation, rain or both, the cup test, soil types
• Colorado State University Extension, PlantTalk 1532: Efficient Lawn Watering
• Nebraska Extension, Irrigation Audits Helpful (2022): about 1 inch a week, 1.5 in the hottest part of summer, catch-can test
• UF/IFAS Extension, ENH9 Watering Your Florida Lawn: 1/2 to 3/4 inch per watering, the 15 minute can test, local limits
• NWS Atlanta/Peachtree City, Explaining "Probability of Precipitation": at least 0.01 inch at a point
• NIST Handbook 44 (2026), Appendix C: 1 square foot = 144 square inches, 1 US gallon = 231 cubic inches

Written by Tobias. Updated October 22, 2026.