DAP Calculator
Calculate DAP needed from your phosphorus (P₂O₅) dose, plus the nitrogen it supplies and the number of 50 kg bags.
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Please note: This calculator provides a mathematical estimate based on the values entered. Recommended agricultural application rates can vary by crop, soil, product formulation, location and official agricultural guidance. Check the product label and local agricultural recommendations before application.
DAP (diammonium phosphate, 18-46-0) is India's most popular phosphorus fertilizer. Enter the P2O5 dose and your field size to find out how many kilograms and bags of DAP you need – and how much nitrogen you're getting along with it.
About the DAP Calculator
DAP carries two nutrients: 18% nitrogen and 46% phosphorus (expressed as P2O5). Because phosphorus is the reason people buy it, the DAP quantity is always calculated from the P2O5 dose. The nitrogen then comes "for free" and should be subtracted from your urea.
This calculator gives you:
- the kilograms of DAP for your field,
- the number of 50 kg bags,
- the nitrogen supplied, so you can reduce urea accordingly.
Phosphorus moves very little in soil, so DAP is normally placed at or before sowing, close to where roots will grow. Drilling it below the seed is far more effective than broadcasting it on the surface.
If you need to plan urea and potash at the same time, the NPK Calculator does all three together.
How to use the DAP Calculator
- 1 Enter your field area and choose the unit.
- 2 Type the P2O5 dose per acre or per hectare from your recommendation.
- 3 Keep 46% unless you are using a different grade.
- 4 Press Calculate. Note the nitrogen supplied – subtract it from your total nitrogen before you work out urea.
The formula we use
Total P₂O₅ (kg) = P₂O₅ dose × area
DAP (kg) = Total P₂O₅ ÷ 46 × 100
Nitrogen supplied (kg) = DAP × 18 ÷ 100
Bags = DAP ÷ 50Shortcut: DAP ≈ P2O5 × 2.17, and every 50 kg bag of DAP gives 23 kg P2O5 and 9 kg N.
Worked example
A 2.5-acre field needs 23 kg P2O5 per acre.
- Total P2O5 = 23 × 2.5 = 57.5 kg.
- DAP = 57.5 ÷ 46 × 100 = 125 kg, which is exactly 2.5 bags (buy 3).
- Nitrogen supplied = 125 × 18% = 22.5 kg N. If the crop needs 100 kg N in total, only 77.5 kg has to come from urea.
Things to keep in mind
- Place it, don't just scatter it. Phosphorus is fixed quickly in most Indian soils. Band placement near the seed improves uptake.
- Avoid seed contact in high doses. DAP releases ammonia as it dissolves, which can damage germinating seed in dry soil. Keep a little soil between seed and fertilizer where possible.
- Consider SSP for oilseeds and pulses. SSP supplies sulphur, which these crops need, and avoids adding extra nitrogen to nitrogen-fixing pulses.
- Check the soil test. Soils that are already high in available phosphorus may need little or none – a soil test can save you the cost of several bags.
Frequently asked questions
What is the full form of DAP?
DAP stands for Diammonium Phosphate. Its grade is 18-46-0: 18% nitrogen, 46% P2O5 and no potash.
How much phosphorus is in one bag of DAP?
A 50 kg bag contains 23 kg of P2O5 and 9 kg of nitrogen.
How do I convert P2O5 to DAP?
Divide the P2O5 by 0.46. For example, 30 kg P2O5 ÷ 0.46 = 65.2 kg of DAP.
Should I reduce urea when I apply DAP?
Yes. Every kilogram of DAP adds 0.18 kg of nitrogen. Subtract that from your nitrogen requirement before calculating urea, or use the NPK Calculator, which does it automatically.
Can I top-dress DAP?
Top-dressing DAP is usually not effective, because phosphorus hardly moves down to the roots. Apply it at or before sowing unless local advice says otherwise.
What if my soil report gives P, not P2O5?
Convert it first: P2O5 = P × 2.29. The P to P2O5 converter does it for you.
Guides that use this calculator
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