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.