Lawn Fertiliser Planner
Get the perfect fertiliser application rate for your lawn. Based on university extension recommendations (Rutgers, Penn State), this calculator uses the standard guideline of 1 lb of nitrogen per 1,000 sq ft (about 4.88 g/m²) to determine exactly how much fertiliser product you need. Simply enter your lawn size, your fertiliser's nitrogen percentage (the first number in the N-P-K ratio like "20-0-0"), and optionally your bag size to know how many bags to buy.
How We Calculate This
Total nitrogen needed = lawn area × target rate. Product mass = total nitrogen ÷ (N% ÷ 100). Bags needed = product mass ÷ bag size, rounded up. Based on university extension recommendations.
Frequently Asked Questions
What is the standard nitrogen application rate?
Most university extension services recommend about 1 lb of actual nitrogen per 1,000 square feet per application. This equals approximately 4.88 g/m². Applying more can burn your lawn and pollute waterways.
What does the N-P-K ratio mean?
N-P-K shows the percentage of Nitrogen (N), Phosphorus (P), and Potassium (K) in the fertiliser. A "20-0-0" product is 20% nitrogen. To get 1 lb of nitrogen, you need 5 lbs of a 20% nitrogen fertiliser.
When should I apply lawn fertiliser?
For cool-season grasses, apply in early fall and late spring. For warm-season grasses, apply in late spring through summer. Avoid fertilising during drought or extreme heat.
Is slow-release fertiliser better?
Slow-release fertilisers reduce the risk of burning and provide steadier nutrition over 6-8 weeks. Quick-release gives faster greening but needs more frequent application and careful dosing.
Related Calculators
You might also find these calculators helpful: Mulch Calculator, and Square Footage Calculator.
Follow all fertiliser label instructions. Over-application can damage lawns and harm the environment. Consider soil testing for precise nutrient recommendations. Local regulations may restrict fertiliser use near waterways.