Fertilizer Calculators
Turn a nutrient recommendation into bags of urea, DAP, MOP and SSP – and work out what it will cost.
Why fertilizer maths trips people up
A soil test report or a Krishi Vigyan Kendra recommendation usually tells you how much nutrient a crop needs – for example 50 kg nitrogen, 25 kg phosphorus (as P2O5) and 12 kg potash (as K2O) per acre. But you don't buy nitrogen at the shop. You buy bags of urea, DAP and MOP, and each of those contains only part of the nutrient you need.
That is where most mistakes happen. Urea is only 46% nitrogen, so 50 kg of nitrogen needs roughly 109 kg of urea, not 50. DAP brings both nitrogen and phosphorus, so if you forget to subtract its nitrogen you end up over-applying urea. These calculators handle that conversion for you.
Which calculator should you use?
- You have an N:P:K recommendation – start with the NPK Calculator. It splits the dose into DAP (or SSP), urea and MOP, and credits the nitrogen already in DAP.
- You only need one fertilizer – use the Urea, DAP, MOP or SSP calculator.
- You are using a mixed grade like 10:26:26 or 12:32:16 – the Fertilizer Requirement Calculator works for any product once you enter its nutrient percentage.
- You want to budget – the Fertilizer Cost Calculator adds up bag prices.
A word on recommendations
These tools do the arithmetic. They don't decide how much nutrient your crop needs – that depends on the crop, variety, soil test values, irrigation and season. For the dose itself, use your Soil Health Card, your state agriculture university's package of practices, or advice from the local agriculture officer.
Frequently asked questions
What is the difference between a nutrient and a fertilizer?
A nutrient is the element the plant uses, such as nitrogen (N), phosphorus (P2O5) or potassium (K2O). A fertilizer is the product that carries it. Urea carries 46% nitrogen, DAP carries 18% nitrogen and 46% P2O5, and MOP carries 60% K2O.
Why are phosphorus and potash written as P2O5 and K2O?
It is the long-standing convention for fertilizer labels and recommendations in India and most of the world. If your soil report gives elemental P or K, convert it first with the P to P2O5 and K to K2O converter.
Do these calculators tell me how much fertilizer my crop needs?
No. They convert a recommended nutrient dose into product quantities. The recommended dose should come from a soil test, your state agriculture university or the local agriculture department.