Fertilizer Calculator

Fertilizer application is based on the desired nutrient rate and the fertilizer’s NPK ratio.

NPK ratio represents the percentage (by weight) of:

• N = Nitrogen (promotes leaf growth)
• P = Phosphorus (promotes roots and flowers)
• K = Potassium (overall plant health)

Imperial (lbs per 1,000 sq ft):

Fertilizer (lbs) = (Desired N rate per 1,000 sq ft / N percentage) × (Area sq ft / 1,000)

For example, to apply 1 lb of nitrogen per 1,000 sq ft with a 10-10-10 fertilizer: Fertilizer = (1 / 0.10) × (Area / 1,000) = 10 lbs per 1,000 sq ft

Metric (kg per 100 m²):

Fertilizer (kg) = (Desired N rate per 100 m² / N percentage) × (Area m² / 100)

For example, to apply 0.5 kg of nitrogen per 100 m² with a 10-10-10 fertilizer: Fertilizer = (0.5 / 0.10) × (Area / 100) = 5 kg per 100 m²

Common lawn fertilizer rates:

• Spring: 0.5–1 lb N per 1,000 sq ft (25–50 g N per m²)
• Summer: 0.5 lb N per 1,000 sq ft (25 g N per m²)
• Fall: 1–1.5 lb N per 1,000 sq ft (50–75 g N per m²)

Common NPK ratios:

• 10-10-10: Balanced, all-purpose
• 20-5-10: High nitrogen for lawns
• 5-10-10: High P and K for flowers/fruit