Fertilizer Calculator
Work out lawn fertilizer from your lawn area and the bag-label rate: product weight, bags to buy, and the actual nitrogen the lawn receives.
Fertilizer is dosed, not poured
Lawn fertilizer is applied by weight per area — the bag's label rate, in pounds of product per 1,000 sq ft, is the dose the manufacturer calibrated its spreader settings around. This calculator starts from that rate and your lawn's area, then works back to the bags, so the lawn gets the feeding the label intends rather than the feeding a guess delivers.
Product needed = area ÷ 1,000 × label rate · Nitrogen applied = product × N% of the analysis
Example: a 5,000 sq ft lawn at a 3 lb per 1,000 sq ft rate needs 15 lb of product — one 15-lb bag, or part of a 40-lb bag with the rest stored dry for the next feeding.
The three numbers on the bag
The analysis — 24-0-6, say — is the percentage by weight of nitrogen, phosphorus (as P₂O₅) and potassium (as K₂O). Enter the first number and the result states the actual nitrogen the lawn receives, per lawn and per 1,000 sq ft, because nitrogen is the nutrient lawn feeding is really about: a healthy single application is typically 0.5 to 1 lb of nitrogen per 1,000 sq ft. More is not better — over-applied nitrogen burns turf, washes into waterways, and is the commonest lawn-feeding mistake there is.
Measure the lawn, not the lot: house, driveway, beds and paths come out of the area, and the square footage calculator will total odd-shaped sections honestly. Calibrate the spreader to the label setting for your model, apply half the product in each of two crossing passes for even coverage, and keep granules off pavement — what lands on concrete feeds the storm drain, not the grass.
Frequently asked questions
How many bags for a 10,000 sq ft lawn?
At the typical 3 lb per 1,000 sq ft rate, 30 lb of product — one 40-lb bag covers it with some left for the next round, or two 15-lb bags almost exactly. The calculator personalizes it to your bag's actual rate, which varies from about 2.5 to 4 lb.
What if I do not know the nitrogen percentage?
Leave it blank — the product and bag counts do not need it. It only powers the nitrogen readout, which is there to keep a feeding honest, not to gate the estimate.
Should I add waste allowance to fertilizer?
A small one covers spreader overlap and the edges you double-pass; 5–10% is plenty. Unlike concrete, extra fertilizer is not harmless if it all goes down — leftover product stores dry for months, so overbuying slightly beats over-applying every time.
When should I fertilize?
Cool-season lawns (fescue, bluegrass, rye) feed best in autumn, then spring. Warm-season lawns (bermuda, zoysia, St Augustine) feed in late spring and summer while they are actively growing. Never onto dormant, frozen or drought-stressed grass.
CalcCoverage