Overseeding a lawn is the process of putting grass seed down on an existing lawn. This can make your lawn greener, fill in sparse or thin areas and reduce weeds or moss growth. Sometimes lawns are overseeded with a different type of seed that is more tolerant of cold weather so the lawn maintains its colour all year. Before overseeding your lawn, you will need to calculate how much grass seed you should buy.

Calculate the square metres of your lawn. You will need the area to determine how much grass seed to buy. To calculate this, measure your lawn with measuring tape then multiply the length by the width.

Determine which type of seed you will be using. There are some variations in amount of seed needed depending on the type of seed used. Not all grass is created equal. The type of seed you chose will depend on your current grass type, geographic location and the type of lawn you would like.

Find out how many pounds of the grass seed you have chosen are needed for your project. Look up the seed type online or visit your local grass seed supplier for this information. Some common types of seed used are Kentucky Bluegrass and Tall Fescue. Kentucky Bluegrass would require one to one and a half kilograms per 100 square metres (two to three pounds for each 1,000 square feet). Tall Fescue would require three to four kilos per square metre (six to eight pounds for each 1,000 square feet).

Calculate the total pounds of seed needed using your calculator. Divide the total area of your lawn by 100. Then multiply that number by the kilos of seed needed per 100 square metres. For example, if you were overseeding with Kentucky Bluegrass and your lawn size was 1,000 square metres, you would do the calculation as follows: 1,000 / 100 = 10; 10 x 1 = 102. You would need at least 10 kilograms (20 lbs) of Kentucky Bluegrass seed to overseed your 1,000 square metre lawn.