Work out how much fertilizer to apply. This free fertilizer quantity calculator sizes the total by product rate, or from a nutrient target and the product’s analysis, with the NPK supplied.
This estimates fertilizer quantities from the rate or nutrient target you enter. The right amount depends on your crop, soil test results and local guidance — over-applying wastes money and can harm waterways. Use a soil test and agronomic advice to set rates.
Fertilizer
kg/ha
kg/ha
%
Enter the area and a product rate to get the total fertilizer needed. Switch to nutrient mode to size the product from a target like kg of N per hectare and the product’s analysis.
Fertilizer needed
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Enter your details
Area (ha)
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Rate
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Total product
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Nutrients (N·P·K)
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By product rate: total = area × rate. By nutrient target: product rate = nutrient target ÷ (analysis ÷ 100). For example, 100 kg N/ha from urea (46% N) needs about 217 kg/ha of urea. NPK supplied is the product applied × each percentage.
Use this free fertilizer quantity calculator to work out how much fertilizer you need. Size it by a product rate, or from a nutrient target and the product’s analysis.
What this fertilizer calculator does
A fertilizer quantity calculator finds the total product for your area. Use a simple rate (kg/ha), or set a nutrient target like kg of N per hectare and let it size the product from the analysis.
How fertilizer quantity is calculated
by rate: total = area × rate
by nutrient: product rate = nutrient target ÷ (analysis % ÷ 100)
nutrients supplied = product × each NPK %
So 100 kg N/ha from urea (46% N) needs about 217 kg/ha of urea — roughly 652 kg over 3 hectares.
Common fertilizer analyses
Fertilizer
N–P–K
Urea
46–0–0
DAP
18–46–0
MOP (potash)
0–0–60
Balanced NPK
e.g. 20–10–10
Why a soil test matters
The right rate depends on your crop, soil reserves and yield goal. A soil test prevents over-applying — which wastes money and can pollute waterways — and under-applying, which limits yield.
How to use the fertilizer calculator
Enter the area and units.
Choose a product rate or a nutrient target + analysis.
Read the total product and nutrients supplied.
Fertilizer Quantity FAQ
How much fertilizer do I need?
Multiply area by the application rate. At 150 kg/ha over 3 hectares you need 450 kg of product.
How do I convert a nutrient target into product?
Divide the nutrient target by the analysis fraction. For 100 kg N/ha from urea (46% N), apply about 217 kg/ha of urea.
What do the NPK numbers mean?
They're the percentages of nitrogen (N), phosphorus (P) and potassium (K) in the product — so 20–10–10 is 20% N, 10% P and 10% K by weight.
How much of each nutrient am I applying?
Multiply the product applied by each percentage. 300 kg/ha of 20–10–10 supplies 60 kg N, 30 kg P and 30 kg K per hectare.
Why should I get a soil test?
It shows what nutrients your soil already holds, so you apply the right amount — avoiding waste, pollution and under-fertilising.
Is the fertilizer calculator free?
Yes, this fertilizer quantity calculator is completely free, needs no sign-up, and gives instant results in your browser.
