Lawn Fertiliser Planner
Example: 500 m² lawn ≈ 12 kg of 20-0-0
Calculate a fertiliser application rate for your lawn. Based on university extension recommendations from Rutgers and Penn State, this calculator uses the guideline of 1 lb of nitrogen per 1,000 sq ft (about 4.88 g/m²). Enter your lawn size, the fertiliser's nitrogen percentage, and optionally the bag size to estimate how much product to buy.
When to apply
Product Needed
Amount of fertiliser product to apply
Bags Needed
Number of bags to purchase
Total Nitrogen
Actual nitrogen being applied
Application Rate
Product per unit area
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.
Methodology last reviewed: July 2024. How SparkCalc works
Sources: Rutgers NJAES Cooperative Extension: How to Calculate the Amount of Fertilizer Needed for Your Lawn (FS839) · Penn State Extension: Calculations Used to Determine the Amount of Fertilizer Needed to Treat Turf · U.S. EPA, Nutrient Pollution: What You Can Do: In Your Yard
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.
Embed this calculator
Add this free calculator to your own website. Copy the code below and paste it into your page’s HTML. It is responsive and resizes to fit.
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.