Fertilizer Calculator: How Much Lawn Fertilizer Per 1,000 Sq Ft

Pounds of product per 1,000 square feet by nitrogen percentage and target rate.

The three numbers are the guaranteed analysis: percent nitrogen (N), percent phosphate (P2O5) and percent potash (K2O) by weight. On a 45 pound bag of 24-6-12, 24 percent of 45 pounds, about 10.8 pounds, is nitrogen, 2.7 pounds is phosphate and 5.4 pounds is potash. Nitrogen drives green color and leaf growth, phosphate supports roots and is most useful when seeding, and potash supports stress tolerance. Many established lawns need little or no phosphate, which is why common maintenance products such as the Lesco Basic Nutrition 32-0-3 Stabilized Nitrogen Fertilizer, 50 lb and the Jonathan Green Green-Up Lawn Food 29-0-3, 15,000 sq ft carry zero. Starter fertilizers such as the Scotts Turf Builder Starter Food for New Grass, 15 lb (24-25-4) are high in phosphate for new seed. The label also lists how much nitrogen is slow release; see how to read a fertilizer label.

• Product per 1,000 sq ft = target pounds of N x 100 / N percent
• Total product = product per 1,000 sq ft x lawn square feet / 1,000
• Bags = total product / bag weight, rounded up
• Phosphate and potash applied = total product x P percent / 100 and x K percent / 100

For a 7,500 square foot lawn fed 0.75 pounds of nitrogen with a 29-0-3 fertilizer: 0.75 x 100 / 29 = 2.6 pounds per 1,000 square feet, times 7.5 = 19.4 pounds of product, a little over one 15,000 square foot bag's worth at half its label coverage. Low-analysis organic products need much more product for the same nitrogen: the Milorganite Slow-Release Nitrogen 6-4-0 Fertilizer, 5 lb Bag (4-Pack) at 6 percent needs about 16.7 pounds per 1,000 square feet for 1 pound of nitrogen, which is why organic programs usually apply less nitrogen more often.

For most homeowners, a product with a good share of slow-release nitrogen is the safer choice. Quick-release nitrogen greens the lawn within days but can surge growth, burn grass if overapplied in heat and wash out faster. Slow-release forms feed over several weeks. Stabilized nitrogen products such as the Lesco Basic Nutrition 32-0-3 Stabilized Nitrogen Fertilizer, 50 lb reduce losses to the air, and balanced professional blends such as the The Andersons Core 24-6-12 Professional Lawn Fertilizer, 45 lb combine forms. Liquid products like the Simple Lawn Solutions Advanced 16-4-8 Liquid Lawn Fertilizer, 1 gal act quickly and are easy to spot-apply, but must be reapplied more often; the trade-offs are in liquid vs granular fertilizer.

Use a broadcast or drop spreader set to the label setting, fill it on a driveway or tarp so spills can be swept up, and apply half the rate in two perpendicular passes. A push broadcast spreader such as the Scotts Turf Builder EdgeGuard DLX Broadcast Spreader covers typical suburban lawns, the EarthWay 2150 Commercial 50 lb Broadcast Spreader handles rough ground, and a tow-behind unit such as the Agri-Fab 130 lb Tow-Behind Broadcast Spreader is the practical choice past half an acre. Sweep or blow any granules off driveways, walks and streets back onto the lawn. See the best lawn spreaders and drop vs broadcast spreaders.