Fertilizer calculator
Turn your nitrogen, phosphorus and potassium targets into kilograms of urea, DAP, MOP and other fertilizers for your field, in your language.
1. Your field
2. Nutrient targets
Enter how many kg of each nutrient your crop needs. Take the numbers from a soil test or your local extension office; the example is only to show the method.
Start from a crop (Bangladesh)
Pick a crop and the soil-test levels from your report, and the targets below are filled in from BARC's official Fertilizer Recommendation Guide 2024. For a fruit tree, pick the crop and the age of the tree instead. You can still change every number.
kg of N
kg of P₂O₅
kg of K₂O
3. Fertilizers you will use
Pick what you can buy locally. The grade is N-P₂O₅-K₂O in percent; choose custom to type the grade printed on your bag.
Bags, nitrogen doses and cost (optional)
Price of one bag of each product, to estimate the cost.
How the calculation works
Fertilizer (kg) = nutrient needed (kg) ÷ nutrient % in the bag × 100
A bag marked 46-0-0 (urea) holds 46% nitrogen, so 46 kg of nitrogen needs 100 kg of urea. P and K on a bag are P₂O₅ and K₂O, so the targets here use those figures. DAP also contains nitrogen, so the calculator counts it before working out the urea.
- 1Choose your area and unit: hectare, acre, decimal or kanal.
- 2Enter how many kg of N, P₂O₅ and K₂O your crop needs per hectare or acre, from a soil test or your extension office.
- 3Pick the fertilizers you can buy. Phosphorus is worked out first, then potassium, then nitrogen, with the nitrogen in DAP subtracted.
- 4Read how many kg and bags of each product to buy, and split the nitrogen into doses.
Worked example (per hectare)
A crop that needs 120 kg N, 60 kg P₂O₅ and 40 kg K₂O per hectare:
| Step | Calculation | Result |
|---|---|---|
| Phosphorus from DAP (18-46-0) | 60 ÷ 46 × 100 | 130 kg DAP |
| Nitrogen already in that DAP | 130 × 0.18 | 23 kg N |
| Nitrogen still needed | 120 − 23 | 97 kg N |
| Urea (46% N) | 97 ÷ 46 × 100 | 211 kg urea |
| Potassium from MOP (0-0-60) | 40 ÷ 60 × 100 | 67 kg MOP |
The calculator keeps the decimals, so it shows about 210 kg of urea; the small difference is rounding. For one acre, divide each figure by 2.47.
Nitrogen is easily lost to water and air, so two or three doses matched to growth stages usually work better than one. Phosphorus and potassium are often applied before or at planting.
Crop doses from Bangladesh's official guide
Pick a crop and the calculator fills in nitrogen, phosphorus and potassium targets from the Fertilizer Recommendation Guide 2024 (FRG-2024), published by the Bangladesh Agricultural Research Council (BARC). It covers 136 crop tables for over 120 crops: boro, aus and aman rice, wheat, maize, potato, mustard, pulses, jute, vegetables, spices, flowers, fodder and fruit trees such as mango, banana, papaya, guava, pineapple, dragon fruit and malta.
The guide does not give one dose per crop. The dose depends on how rich your soil already is, so you choose the soil-test level (very low, low, medium or optimum) for nitrogen, phosphorus and potassium from your soil-test report. The calculator uses the middle of the guide's range and shows the range beside it.
The guide lists phosphorus and potassium as the elements, per hectare. The calculator converts them to P₂O₅ and K₂O, the form printed on fertilizer bags, and still works out your field in acres or hectares (and in bigha, katha and shatak when you use the Bangla version).
By default the nitrogen already contained in DAP is not subtracted, as in the guide. You can switch this on to see how much less urea you would need.
Fruit trees are different: the guide gives grams per tree for each age of the tree, so you enter how many trees you have and how old they are. Banana and papaya are dosed per plant for the pit and each top dressing.
Crops included
Wheat and maize
Oilseeds
Root and tuber crops
Vegetables
- Cauliflower
- Cabbage
- Tomato
- Tomato (summer)
- Okra
- Radish
- Bitter gourd
- Cucumber
- Broccoli
- Chinese cabbage
- Batisak
- Kangkong (Kolmi shak)
- Spinach (Palong shak)
- Amaranth (Danta shak)
- Country bean (Sheem)
- Yardlong bean (Borboti)
- French bean (Jhar sheem)
- Garden pea (Motorshuti)
- Sweet gourd (Misti kumra)
- Ash gourd (Chal kumra)
- Teasle gourd (Kakrol)
- Pointed gourd (Potol)
- Sponge gourd (Dhundul)
- Squash
- Sweet pepper (Capsicum)
Fruits
- Pineapple (Anarosh)
- Strawberry
- Watermelon (Tormuj)
- Netted melon (Cantaloupe)
- Mango (Aam)
- Jackfruit (Kanthal)
- Banana (Kola)
- Papaya (Pepe)
- Guava (Peyara)
- Coconut (Narikel)
- Litchi (Lichu)
- Pummelo (Batabi lebu)
- Mandarin orange (Komola)
- Sweet orange (Malta)
- Lemon (Lebu)
- Satkara
- Jujube (Boroi, Kul)
- Golden apple (Amra)
- Sapota (Sofeda)
- Star fruit (Kamranga)
- Black plum (Jam)
- Burmese grape (Lotkon)
- Indian gooseberry (Amloki)
- Wax apple (Jamrul)
- Bael (Bel)
- Wood apple (Kodbel)
- Bullock's heart (Ata)
- Custard apple (Sharifa)
- Velvet apple (Bilati gab)
- Tamarind (Tetul)
- Elephant apple (Chalta)
- Dragon fruit
- Longan
- Cashew nut (Kajubadam)
- Star gooseberry (Orboroi)
- Fig (Dumur)
- Indian olive (Jalpai)
Spices
Sugarcane, betel and palms
Flowers
This is the Bangladesh guide. It is not a blanket recommendation: ask your local agriculture extension officer, and use a soil test whenever you can. Soil that tests High or Very high is not covered by the guide's tables.
Fertilizer calculator questions
How do I calculate urea per acre?
Work out the nitrogen your crop needs per acre, divide by 46 and multiply by 100. For 50 kg of N per acre that is about 109 kg of urea.
How many kg of DAP per hectare?
Divide the phosphorus target in kg of P₂O₅ by 46 and multiply by 100. For 60 kg of P₂O₅ per hectare that is about 130 kg of DAP.
Why does DAP reduce the urea I need?
DAP contains 18% nitrogen as well as phosphorus. That nitrogen counts towards your target, so the calculator subtracts it before working out the urea.
What do P₂O₅ and K₂O mean on a fertilizer bag?
They are the standard way of stating phosphorus and potassium. A 0-0-60 bag holds 60% K₂O, so calculate with that figure rather than treating it as pure potassium.
Does this replace a soil test?
No. The calculator only turns targets into kilograms. A soil test tells you which nutrients are actually low, so you add only what the soil lacks.
How much DAP, urea and MOP does rice need per bigha or acre in Bangladesh?
It depends on the rice type (boro, aus or aman), your yield goal and your soil-test levels. Choose the crop and your soil levels in the calculator and it fills in the official BARC range, then works out kg of urea, DAP and MOP for your field in acres or hectares (or in bigha in the Bangla version).
Where do the crop doses come from?
From the Fertilizer Recommendation Guide 2024 (FRG-2024) of the Bangladesh Agricultural Research Council (BARC). The numbers are read from the guide's crop tables and checked against the book. They are for Bangladesh and are not a blanket recommendation.
How many decimals (shatak) are in one bigha?
The common Bangladesh bigha is 20 katha, which is about 33 decimal (shatak), 1,337.8 square metres or 14,400 square feet. One acre is 100 decimal. The calculator takes your land in bigha, katha, chhatak, decimal, acre, hectare or square metres and converts it for you. Land measures differ a little between regions, so use the area you actually measured if you know it.
TSP or DAP: which should I use?
Both carry the same 46% phosphate (P₂O₅), so the phosphorus dose is the same weight of either. DAP also has 18% nitrogen, so you can use a little less urea with it; TSP has no nitrogen. Use one or the other for the same phosphorus dose, not both. Choose by price per kilogram and by what your dealer has in stock.