Lawn Fertilizer Calculator
How much fertilizer does your lawn actually need?
How this is calculated
- Nitrogen needed = (lawn area ÷ 1000) × N rate per 1000 sq ft
- Product pounds = nitrogen needed ÷ (product N % ÷ 100)
- The N % is the first number of the fertilizer analysis printed on the bag (e.g. 32-0-10)
Common questions
How much fertilizer do I need for 5000 sq ft?
At the standard 1 lb of nitrogen per 1000 sq ft, a 5000 sq ft lawn needs 5 lb of nitrogen. With a common 32-0-10 product (32% N), that is 15.6 lb of fertilizer — about one and a half standard 15 lb bags.
What do the three numbers on a fertilizer bag mean?
N-P-K: nitrogen (green growth), phosphorus (roots — often 0; many states restrict it), and potassium (stress tolerance). A 32-0-10 bag is 32% nitrogen by weight, so a 15 lb bag contains 4.8 lb of actual nitrogen.
How often should I fertilize my lawn?
Cool-season grasses (fescue, bluegrass): primarily fall, with a light spring feed — 2-3 total applications at 0.75-1 lb N each. Warm-season (bermuda, zoysia, St. Augustine): late spring through summer. Never exceed ~1 lb N per 1000 sq ft per application; more risks burn and disease.
How do I measure my lawn area?
Walk it off: a normal adult pace is roughly 2.5 ft. Or use the house footprint: most quarter-acre lots have 4000-7000 sq ft of actual turf after the house, driveway, and beds. Precision is nice but fertilizer forgiving within ±10%.
Is slow-release fertilizer different for the math?
The bag math is identical — the N % on the label is what counts. Slow-release just meters the nitrogen out over 8-12 weeks, which is gentler (less burn) and feeds longer. Synthetic quick-release at high rates can burn; if you are unsure, halve the rate and reapply in a month.