Glyphosate herbicides such as Roundup are broad spectrum, meaning they'll kill all vegetation on which they're sprayed. Using Roundup on your lawn is one of the fastest ways to kill the grass, whether you want to kill your grass to make room for new shrubs, a new variety of grass or a walkway or garden structure. Avoid more labor-intensive methods like sod cutting and spray your yard with Roundup to start seeing results within a week.
Avoid watering the grass for 24 hours before applying the Roundup to ensure a dry environment that will allow the Roundup to penetrate the grass at full strength. Wait for a dry day when there's little to no chance of rain.
Pour the Roundup Ready-to-Use product into a garden sprayer, if needed; some bottles of Roundup include a built-in spray applicator.
Mist the Roundup product onto the grass, applying an even mist onto all exposed grass surfaces. Start at one end of the lawn and walk away from the direction of the spray to ensure that you don't walk on the freshly sprayed herbicide.
Wait for the Roundup to kill the grass. Brown and wilting grass will begin appear within six hours of applying the Roundup Ready-to-Use product, according to Monsanto, manufacturer of Roundup.