Calculate the total quantity of fertilizer needed for your field, and how much to apply per split, based on your land area and recommended dose.
How to Use the Fertilizer Calculator
Enter your "Land Area (acres)".
Enter the "Recommended Dose (kg/acre)" for your crop - get this from your local agriculture extension office, soil test report, or seed packet instructions.
Enter the "Number of Applications/Splits" you plan to divide the dose into over the season.
Click "Calculate" to see the total fertilizer needed and the quantity for each application.
What the Calculator Does
It scales a per-acre dose to your field and divides it equally across the number of applications: Total Fertilizer (kg) = Land Area (acres) × Dose (kg per acre), and Quantity per Application = Total ÷ Number of Splits.
The dose you enter must be kg of the actual product you will buy, such as urea or DAP. Soil health cards and crop recommendations usually give nutrients instead, as kg of N, P₂O₅ and K₂O. Those numbers have to be converted to product quantities first, as shown below.
Nutrient Content of Common Fertilizers
Fertilizer
Nutrient content
Product needed for 1 kg of nutrient
Urea
46% N
about 2.17 kg per kg of N
DAP (diammonium phosphate)
18% N, 46% P₂O₅
about 2.17 kg per kg of P₂O₅
SSP (single super phosphate)
16% P₂O₅
6.25 kg per kg of P₂O₅
MOP (muriate of potash)
60% K₂O
about 1.67 kg per kg of K₂O
Grades of complex NPK fertilizers vary by product. Read the grade printed on the bag, for example 10:26:26, which means 10% N, 26% P₂O₅ and 26% K₂O.
Worked Example: From Nutrients to Bags
Say the recommendation for your crop is 48 kg N, 24 kg P₂O₅ and 16 kg K₂O per acre, and you farm 3 acres.
Phosphorus first, from DAP: 24 ÷ 0.46 ≈ 52 kg DAP per acre. This also supplies 52 × 0.18 ≈ 9.4 kg of nitrogen.
Remaining nitrogen from urea: 48 − 9.4 = 38.6 kg N, and 38.6 ÷ 0.46 ≈ 84 kg urea per acre.
Potash from MOP: 16 ÷ 0.60 ≈ 27 kg MOP per acre.
Enter each product separately. For urea: 3 acres, 84 kg per acre, 3 splits gives a total of 252.00 kg and 84.00 kg per application. Urea is sold in 45 kg bags, so that is 5.6 bags; buy 6.
For DAP: 3 acres at 52 kg per acre with 1 split gives 156.00 kg, a little over three 50 kg bags. MOP comes to 81 kg for the field.
Planning Split Applications
Nitrogen moves easily with water and can be lost by leaching or as gas, so it is usually given in two or three doses timed to the crop's growth. Phosphorus and potash stay where they are placed in the soil, so they are commonly applied in full at sowing as a basal dose.
This calculator splits the total into equal parts. Many recommendations use unequal splits, such as half the nitrogen at sowing and a quarter at each of two later stages. In that case, take the total from the calculator and work out each share yourself: for 252 kg of urea, half is 126 kg and each quarter is 63 kg.
Practical Tips
Base the dose on a recent soil test. Under the Soil Health Card scheme, samples can be tested through government soil testing labs, and the card lists crop-wise fertilizer recommendations.
Count manure and compost. Farmyard manure supplies some nutrients, and recommendations often allow a lower chemical dose where it is used.
Apply urea top dressing when the soil is moist, not just before heavy rain, so less is washed away.
Do not mix up product and nutrient figures. Entering 48 kg of N as 48 kg of urea would give the crop less than half the nitrogen it needs.
Frequently Asked Questions
The correct fertilizer dose depends heavily on your soil's existing nutrient levels, crop variety, and local growing conditions - a generic recommendation could easily be wrong for your field. Always use a soil test report or your local agriculture extension office's recommendation as the input dose here.
Splitting the total dose across the growing season (e.g. at sowing, tillering, and flowering) helps match nutrient availability to the crop's actual uptake needs at each stage, and reduces nutrient loss compared to applying everything at once.
Yes - as long as your "Recommended Dose" is expressed as kg of that specific fertilizer product (like Urea, DAP, or a blended NPK product) per acre, this calculator scales it to your total land area.
Convert each nutrient into a product quantity first by dividing by the nutrient share of the fertilizer. For example, 46 kg of N from urea (46% N) is 46 ÷ 0.46 = 100 kg of urea. Enter that product figure as the dose, and run the calculator once for each fertilizer.
Divide the total fertilizer shown by the bag size and round up. Neem-coated urea is sold in 45 kg bags in India, so 252 kg needs 6 bags. Check the bag weight printed on the product you buy, as other fertilizers come in different sizes.