Nitrogen rate and cost per kg N calculator
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About this calculator
Enter a yield target and your soil test result to see how much of a nitrogen product to spread, and what each kilogram of nitrogen costs. It runs in your browser; nothing you type is sent anywhere.
General information only. Check with your agronomist or local advisor. More
Assumptions, in plain words
- Crop N need = expected yield × 40 kg N per t/ha for wheat and barley, or × 80 for canola. This is GRDC’s rule of thumb for soil plus fertiliser N, applied to “economic yield” (about 80% of water-limited potential yield).
- Fertiliser N = crop N need − soil mineral N − N already applied. If that is below zero we show zero.
- Product rate = fertiliser N ÷ N fraction of the product (urea 0.46). With a loss allowance, we also divide by (1 − loss). That last step is our arithmetic, not part of the GRDC method.
- Cost per kg of N = price per tonne ÷ (10 × N%). Prices are yours; we only pre-fill an indicative urea listing if you click the button. See how it works.
- Not included: soil-test error (can be 20–40 kg/ha N or more), in-crop mineralisation, timing and splitting, freight, spreading, GST, other nutrients, and crops other than wheat, barley and canola.
Want the arithmetic by hand? Read how much urea per hectare for wheat and the step-by-step N budget. To compare products with soil-based loss ranges, use the comparison tool.
Sources
- Back to nitrogen basics – soil testing and nitrogen budgeting fundamentals (GRDC 2024)
- Volatilisation of surface-applied urea on Queensland Vertosols: how much nitrogen is lost and what drives it? (GRDC 2026)
- Nitrogen loss pathways. How much N is lost when urea is not mechanically incorporated after application? (GRDC 2021)
- Farm Inputs (Farm Tender) fertiliser listings: Urea ex Geelong, Brisbane, Port Kembla, Newcastle; SOA ex Geelong (Farm Tender (commercial listing page) 2026)
Last updated 17 October 2026.