Lawn grass fertilizers are primarily nitrogen plus smaller amounts phosphorous and potassium. The three numbers found on each fertilizer package (for example 30-2-3) indicates the percentage of each of these key nutrients. The first number (usually 25 to 35) indicates the percentage of nitrogen. Use the calculator below to see how many pounds of fertilizer you need to apply each year to keep your lawn healthy. In most cases, you would apply one-half to one-third of this amount in each of two or three well-spaced applications during the growing season.

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Lawn fertilizer calculator

Enter the requested information below, then click Calculate to see the range of amounts of fertilizer you need annually. Remember, too much fertilizer is just as damaging as too little.

Square feet to be fertilized Percent nitrogen in the fertilizer Type of grass (check one)
Fescue Kentucky Bluegrass, Ryegrass Bermuda Bahi St. Augustine Pounds of fertilizer needed per year:
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Please note: For your convenience, this calculation has been rounded up slightly.

Important reminder: Every effort has been made to ensure the accuracy of this calculation. But before purchasing materials for any project, please check amounts with your suppliers or contractors.

Helpful Tips

• Bags of fertilizer always provide a recommended application rate. This calculator will also provide the details you need.
• Most lawns need regular feeding -- once or twice a year -- if they are to be lush and healthy. Feed cool-season grass (grass that generally stays green all year and grows primarily in the South) in the spring and autumn; feed warm-season grass (the Northern grasses that go dormant in the fall and winter) in the spring and summer.
• Apply fertilizer with a spreader, for even distribution. A lawn's greatest need is for nitrogen, so the amount of fertilizer you need will depend on the nitrogen content of the fertilizer.