How to use this calculator
- Enter Lawn area in sq ft.
- Enter Nitrogen % (first number).
- Enter Target N per 1000 sq ft in lb.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
Standard feeding = 1 lb of actual nitrogen per 1,000 sq ft. Product needed = target N ÷ (bag N% ÷ 100). A 25-5-10 bag delivers 1 lb N per 4 lb of product. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Where this fits in the project
Hardscape follows the same layer logic as paving: excavate, place compacted base and bedding sand, then set surface units. Bulk organics like mulch and topsoil are ordered by the cubic yard.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the fertilizer calculator:
- Grass Seed Calculator — Starter fertilizer applied when seeding.
- Sod Calculator — New sod requires starter fertilizer.
- Topsoil Calculator — Fertilizer is applied to topsoil for plant nutrition.
- Compost Calculator — Compost provides organic nutrients vs synthetic fertilizer.
- Mulch Calculator — Fertilizer feeds plants; mulch protects soil.
Frequently asked questions
What does 25-5-10 mean?
Percent by weight of nitrogen, phosphate and potash — a 50 lb bag of 25-5-10 contains 12.5 lb of actual N.
How often should lawns be fertilized?
2–4 applications per year at ~1 lb N each, timed to the grass type’s growth season — not summer for cool-season turf.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.