Turf: Lawn Care Calculator
The lawn-care calculator that doesn't sell you fertilizer — just the math, every number cited.
What it does
Most "lawn apps" are a funnel for one brand's products. Turf is a neutral, citation-backed tool that just does the math: how much nitrogen, how much seed, how much lime, what spreader setting, what dilution. The hero nitrogen-rate calculator is free forever at full citation quality — enter your bag's N-P-K, target rate, and lawn size, and get product per 1,000 sq ft, bags needed, and a hard guardrail at the ~1.0 lb N per 1,000 sq ft single-application cap (Purdue, Virginia Cooperative Extension).
A one-time $4.99 Turf Pro purchase unlocks five more calculators — spreader calibration (weigh-back method), liquid dilution / tank-mix, lime & sulfur pH amendment by soil texture, grass seed rate by species, and PGR growing-degree-day timing on the Kreuser & Soldat model. No subscription, no ads, no account, works offline.
Turf is honest by design: it shows its work and flags what's disputed — where a popular lime table isn't in any primary extension publication, or where a GDD target is validated for putting greens rather than home lawns, Turf says so plainly. Sources include Purdue Turfgrass, Penn State Extension, Michigan State, University of Minnesota, NC State, Cornell, Texas A&M AgriLife, Clemson HGIC, and the US EPA. For any pesticide or plant-growth regulator, the label is the law.