Fertilizer Rate Calculator

Two steps, then the buy-list. First we work out how much of this product delivers your target nitrogen rate per 1,000 sq ft; then we scale that to your whole lawn and round up to whole bags. The same ratio applied to the phosphate and potash numbers gives the P₂O₅ and K₂O you co-deliver.

step 1 — product per 1,000 sq ft:
  lbs/1,000 = target N ÷ (N% ÷ 100)

step 2 — scale to the lawn:
  total lb  = lbs/1,000 × (area sq ft ÷ 1,000)

bags (when a bag size is given):
  bags      = ceil(total lb ÷ bag lb)
  leftover  = bags × bag lb − total lb

co-delivered (oxide basis, same N formula):
  P₂O₅/1,000 = lbs/1,000 × (P% ÷ 100)
  K₂O/1,000  = lbs/1,000 × (K% ÷ 100)

The second and third numbers on a bag are P₂O₅ (phosphate) and K₂O (potash) on an oxide basis — not elemental P and K — so we keep those labels to match the bag and every cited source. Bags always round up: you can't buy a fraction of a bag.

The nitrogen-rate note is general reference, not a rule. Single-application guidance lands around 0.9–1.0 lb N / 1,000 sq ft for quick-release nitrogen and roughly 3.25 lb N / 1,000 sq ft per year, but caps vary by state, turf type, and your soil test. The math follows Omni Calculator, Rutgers FS839, Purdue Turfgrass Science, and UNH Extension (see Sources below).