Roundup is an all-purpose weed killer that can take out some tough vegetation. It is used quite a bit by both homeowners and commercial landscapers. It is a dangerous chemical, however, so you must be careful when using it. If you are not certified to apply chemicals to lawns, then you should follow the directions as they come on the bottle and don't try to make it stronger.
Get a tablespoon, cup or quart measuring device depending on how much you want to mix and the strength that you want. The stronger the mix the more potent the roundup is. Use a tank for large spray jobs or a spray bottle to mix small amounts. Do not use steel if it is not lined. The only exception is stainless steel.
Add about half of the water needed for your mix.
Add the roundup portion. For a 1-gallon mix add any where from 1 tbsp. to 18 tbsp. for a strength of 0.4 percent to 7 percent. For 25 gallons add from 1 1/2 cups up to 7 quarts of Roundup for the same range of strengths. And for 100 gallons add 1.6 quarts to 7 gallons.
Add the rest of the water.
Stir the mixture to make sure that the product is spread throughout the container.