Fertiliser Requirement Calculator

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

About Fertiliser Requirement Calculator

Divides the nutrient target by the fertiliser's nutrient content to give the product rate, then scales to the area and cost.

Formula

Fertiliser rate

Product rate (kg/ha) = nutrient target (kg/ha) / nutrient content fraction; urea at 46% N needs 2.17 kg per kg of N

Worked example

With the default values below, Fertiliser Requirement Calculator returns Fertiliser per hectare of 260.87. Change any input above and every figure here is recalculated in your browser.

Inputs used

Nutrient to applyaccepts 1–1,000 kg/ha: 120 kg/ha
Nutrient content of the fertiliseraccepts 1–100: 46
Areaaccepts 0.01–100,000 ha: 3 ha
Fertiliser price per tonneaccepts 1–10,000: 500

Results

Fertiliser per hectare: 260.87 kg/ha
Total fertiliser required: 782.61 kg
50 kg bags required: 15.65
Fertiliser cost: $391.30

Step by step

1Values used
2Fertiliser rate
3Fertiliser per hectare= 260.87 kg/ha
4Total fertiliser required= 782.61 kg
550 kg bags required= 15.65
6Fertiliser cost= 391.30

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, fees or charges or compounding frequency 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 does urea need 2.17 kg per kg of nitrogen?

It contains 46% nitrogen, so one divided by 0.46 gives 2.17.

Should phosphate be expressed as P or P2O5?

Fertiliser labels use P2O5 and K2O; multiply P by 2.29 and K by 1.2 to convert to oxide basis.