Fertiliser Quantity Calculator
Turns a nutrient recommendation into a weight of fertiliser to spread.
Fertiliser rate
— kg/ha
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Fertiliser rate — lb/acre
For a garden — g/m²
Fertiliser for the whole area —
Bags —
What that rate supplies
Reading this —
The formula
product rate = nutrient wanted ÷ (grade % ÷ 100)
A 20% N fertiliser is one-fifth nitrogen by weight, so it takes 5 kg of product for each kilogram of nitrogen.
What to watch out for
The three grade numbers are percentages by weight of N, P₂O₅ and K₂O. Most labels use these, but some countries label phosphorus and potassium as the elements: the NPK ratio calculator converts between them.
Frequently Asked Questions
How much 20-10-10 supplies 60 kg of nitrogen per hectare?
300 kg/ha, which also supplies 30 kg/ha each of P₂O₅ and K₂O.
How much fertiliser per square metre?
Divide kg/ha by 10 to get g/m². 300 kg/ha is 30 g/m².