Current for 2026•As of: July 2026

Lawn Fertilizer Calculator calculate application rate.

Calculate the fertilizer amount needed from area, application rate and nitrogen content (NPK)

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Lawn Fertilizer Calculator

Calculate the fertilizer amount needed from area, application rate and nitrogen content (NPK) – for spring and autumn.

Season

Nitrogen-heavy starter feeding after the winter break for fast growth (e.g. NPK 20-5-8)

Typical range for Spring: 25–35 g/m²

First number of the NPK figure on the fertilizer packaging, e.g. 20 for "20-5-8"

Fertilizer amount needed

3.00 kg

100 m² × 30 g/m² (Spring)

Total pure nitrogen

600 g

Pure nitrogen per m²

6.00 g/m²

Fertilizer amount

3.00 kg

Tip: Never apply more than 4–6 g of pure nitrogen per m² per single feeding – with a higher annual requirement, spread it over several applications to avoid scorch damage.

Dosing lawn fertilizer correctly

Too little fertilizer barely works, too much can damage the lawn and harm the environment

The formula is simple: fertilizer amount (kg) = area (m²) × application rate (g/m²) ÷ 1,000. From the NPK figure on the packaging you can also calculate how much pure nitrogen is applied: pure nitrogen (g/m²) = application rate (g/m²) × nitrogen content (N%) ÷ 100.

Spring vs. autumn: Spring fertilizers are nitrogen-heavy (e.g. NPK 20-5-8) and stimulate growth after the winter break – typical application rate 25–35 g/m². Autumn fertilizers are potassium-heavy (e.g. NPK 8-5-15) and prepare the lawn for winter with less nitrogen – typical application rate 20–30 g/m².

Upper limit per application: Even with a high annual requirement, no more than 4–6 g of pure nitrogen per m² should be applied per single feeding. If the calculated annual requirement is high, it makes more sense to spread the feeding over several dates across the season instead of overdosing in one go.

Application rates at a glance

Typical application rates by season

Spring: 25–35 g/m²
Nitrogen-heavy starter feeding, e.g. NPK 20-5-8
Autumn: 20–30 g/m²
Potassium-heavy winter prep, e.g. NPK 8-5-15

Calculation example

Lawn area 100 m², spring fertilizer NPK 20-5-8, 30 g/m²

Lawn area 100 m², spring fertilizer NPK 20-5-8, 30 g/m²
ItemAmount
Area100 m²
Application rate30 g/m²
Total fertilizer amount3.00 kg
Pure nitrogen per m² (30 × 20%)6.00 g/m²
Total pure nitrogen600 g

Frequently asked questions about the lawn fertilizer calculator

Everything about application rate, NPK values and feeding times

In spring, 25–35 g/m² is typical (nitrogen-heavy fertilizer for fast growth), in autumn 20–30 g/m² (potassium-heavy fertilizer for frost resistance). The exact application rate is always printed on the product packaging and takes precedence over these guide values.

NPK stands for the three main nutrients nitrogen (N), phosphorus (P) and potassium (K). The numbers give the percentage content in the fertilizer, e.g. "20-5-8" means 20% nitrogen, 5% phosphorus and 8% potassium. Spring fertilizers usually have a high N value, autumn fertilizers a higher K value.

No more than 4–6 g of pure nitrogen per m² should be applied per single feeding, otherwise scorch damage can occur. The annual requirement is 10–15 g N/m² for ornamental lawns and 18–25 g N/m² for heavily used play lawns – spread across several applications during the season.

Spring fertilizer is nitrogen-heavy and promotes fast root and blade growth after winter. Autumn fertilizer is potassium-heavy: potassium strengthens cell walls and increases frost resistance, without stimulating sensitive growth shortly before winter through too much nitrogen.

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