Fertilizer Calculator
Tell it your lawn size, how much nitrogen you're after, and the nitrogen percent on the bag — and it hands back exactly how many pounds of product to spread.
That first number on the bag — like the 26 in 26-0-3 — is the nitrogen percentage. One pound of N per 1,000 sq ft is a typical single feeding.
How it works
Fertilizer feeding rates are set by nitrogen, and that first number in the N-P-K on the bag is the nitrogen percent. A 26-0-3 bag is 26 percent nitrogen, so every pound of product carries 0.26 lb of actual N.
To hit a target like 1 lb of N per 1,000 sq ft, we divide the target by the nitrogen fraction — 1 divided by 0.26 is about 3.85 lbs of product per 1,000 sq ft. Then we scale that up to your lawn's real area.
Applying by actual nitrogen keeps you from over- or under-feeding when you switch brands. Two bags with different numbers can need very different amounts of product to deliver the same pound of N.
Frequently asked questions
How do I read the numbers on a fertilizer bag?
The three numbers are N-P-K — nitrogen, phosphorus, potassium — as percentages by weight. For feeding rates, the first number is what matters; a 26-0-3 bag is 26 percent nitrogen.
How much nitrogen does a lawn need?
About 1 lb of actual nitrogen per 1,000 sq ft per feeding is a safe, common target, spread across a few applications through the season rather than dumped all at once.
Why calculate by nitrogen instead of just following the bag?
Bag directions assume one product. Working from actual nitrogen lets you apply any fertilizer at the right rate, so a 46-0-0 and a 10-10-10 both land you the same pound of N.
Can I put down too much?
Absolutely, and it shows — over-applying nitrogen burns the grass, pushes soft growth that pests love, and runs off into storm drains. When in doubt, go light and feed again later.