Lawn Fertiliser Quantity Calculator

Work out lawn fertiliser quantity instantly with clear inputs, formula shown and shareable results.

About Lawn Fertiliser Quantity Calculator

Fertiliser is dosed on nutrient, not product: divide the nitrogen target by the product's nitrogen percentage to get the product weight. A 25 g per square metre annual nitrogen target from a 12% product means about 208 g of product per square metre, split across the season.

Formula

Fertiliser rate

product = area x nitrogen target / (N content); split across the number of applications

Worked example

With the default values below, Lawn Fertiliser Quantity Calculator returns Product per application of 12.50. Change any input above and every figure here is recalculated in your browser.

Inputs used

Lawn area: 180 m²
Nitrogen target: 25 g/m²
Nitrogen content of the product: 12 %
Applications per year: 3 applications

Results

Product per application: 12.50 kg
Annual product required: 37.50 kg
Application rate: 69.44 g/m²
Nitrogen per application: 8.33 g/m²

Step by step

1Values used
2Fertiliser rate
3Product per application= 12.50 kg
4Annual product required= 37.50 kg
5Application rate= 69.44 g/m²
6Nitrogen per application= 8.33 g/m²

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why split into several applications?

A single heavy dose burns the grass and leaches into groundwater. Three to four light feeds through the growing season give steadier growth and less loss.

What do the NPK numbers mean?

Percentages by weight of nitrogen, phosphorus pentoxide and potassium oxide. A 12-4-8 product is 12% N, so it takes 8.3 kg to deliver 1 kg of nitrogen.