Turf: Lawn Care Calculator

Turf is the lawn-care calculator that doesn't sell you fertilizer. 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. Every number cites a named university turf-extension source. No account, no ads, no subscription, works offline.

NITROGEN RATE (FREE, FOREVER)
Enter your bag's N-P-K analysis, your target nitrogen rate, and your lawn size. Turf returns pounds of product per 1,000 sq ft and for the whole lawn, bags needed, and a slow-release advisory — with a hard guardrail if you exceed the roughly 1.0 lb N per 1,000 sq ft single-application cap (Purdue, Virginia Cooperative Extension). The hero calculator is free forever, at full citation quality.

TURF PRO (ONE-TIME $4.99, NO SUBSCRIPTION)
A single $4.99 purchase unlocks the other five calculators — pay once, keep forever, restore across your devices:

- Spreader calibration — the weigh-back method to dial any spreader to your target rate, because the settings printed on the bag are starting points, not guarantees (Penn State).
- Liquid dilution / tank-mix — convert a product's label rate into ounces per gallon and per 1,000 sq ft, driven by your real, measured sprayer output (US EPA, extension calibration method).
- Lime & sulfur pH amendment — pounds per 1,000 sq ft to raise pH with lime or lower it with elemental sulfur, by soil texture (sand / loam / clay), with per-application caps (Michigan State, Penn State, Clemson HGIC, University of Minnesota, NC State).
- Grass seed rate — pounds of seed per 1,000 sq ft, new seeding vs. overseed, by species: KBG, tall fescue, perennial ryegrass, fine fescue, bermuda, zoysia, centipede (Penn State, Cornell, Texas A&M).
- PGR growing-degree-day timing — accumulate GDD to time your next Primo Maxx / T-Nex (trinexapac-ethyl) application, on the Kreuser & Soldat model.

HONEST BY DESIGN
Turf shows its work and flags what's disputed. The popular "sand 25 / loam 75 / clay 100" lime table isn't in any primary extension publication, so Turf uses the documented turf topdress band instead — and tells you so. The 200-GDD PGR target is validated for golf putting greens, not home lawns, so Turf says that plainly rather than pretending it's universal. For any pesticide or plant-growth regulator, the law is the product label.

SOURCES
Purdue Turfgrass, Virginia Cooperative Extension, Clemson HGIC, Penn State Extension, Michigan State University, University of Minnesota, NC State, Cornell, Texas A&M AgriLife, US EPA, and Kreuser & Soldat (PGR growing-degree-day model).

DISCLAIMER
Turf is an educational reference calculator, not professional agronomic or pesticide-application advice. Always follow the product label and confirm rates with your local cooperative extension office. For any pesticide or plant-growth regulator, the label is the law: it is a violation of federal law to use a product in a manner inconsistent with its labeling (US EPA).

Free download includes the full nitrogen-rate calculator. Turf Pro is a single one-time purchase ($4.99) that unlocks spreader calibration, liquid dilution, lime & sulfur, seed rate, and PGR timing. No subscription, no ads, no account.