Nitrogen Cost Comparison Calculator

Each product converts to cost per pound of actual nitrogen the two-step way the extension guides teach it: pull the nitrogen out of the bag, then divide the price by it. We rank ascending on the full-precision $/lb N (never the rounded cents), so two products that display the same price can't flip the winner. Coverage and cost per 1,000 sq ft respond to your target rate.

per product:
  weight_lb         = per ton ? (tons × 2,000) : bag weight (lb)
  lb N              = weight_lb × (N% / 100)
  cost per lb N     = price / lb N
  coverage (sq ft)  = (lb N / target N rate) × 1,000
  cost / 1,000 sqft = cost per lb N × target N rate

ranking:
  valid rows  = price > 0 AND weight > 0 AND 0 < N% ≤ 82
  ranked      = valid rows, ascending by cost per lb N
  best        = ranked[0]  (cheapest nitrogen)
  savings vs next = (next.$/lbN − best.$/lbN) / next.$/lbN

Worked example: a 50 lb bag of 21-7-14 at $22 holds 50 × 0.21 = 10.5 lb N, so $22 / 10.5 = $2.10 / lb N, covering 10,500 sq ft at 1 lb N / 1,000 sq ft. The two-step method is NMSU Extension Guide A-133; the per-1,000-sq-ft turf framing follows Horizon. 1 US short ton = 2,000 lb. Slow-release value and agronomic fit are not part of this number.

Cost per pound of nitrogen answers which bag to buy. It does not say how much to put down or what the visit is worth. The rate math that turns a target nitrogen rate into bag weight handles the first question, a catch test on the spreader confirms the machine agrees with it, and the price of a full season of treatments answers the second.