How to calculate the cost per kg of nitrogen (with examples)

The formula

A tonne is 1,000 kg, and N% is the share of the product that is nitrogen. So one tonne of a 46% N product holds 1,000 × 0.46 = 460 kg of N. Divide the price by that: $820 ÷ 460 = $1.78 per kg of N. The shortcut is price ÷ (10 × N%), where N% is written as 46.

Worked examples

The prices below are the only ones in our data: third-party asking prices for bulk urea, read on 17 October 2026, ex GST, with no listing date, no freight and no spreading. They are not quotes and may be out of date.

The 8.1% is the median in-crop ammonia loss in a GRDC summary of Australian field measurements (range 0–29%). Your own loss could be near zero or several times higher, depending on soil, weather and whether the urea is incorporated. See urea volatilisation.

Adjusting for losses: the effective cost

Effective cost per kg of N delivered = cost per kg N ÷ (1 − loss). At 8.1% loss, $1.78 becomes $1.78 ÷ 0.919 ≈ $1.94. This is simple arithmetic, and it only covers ammonia loss, not leaching, immobilisation or timing.

Comparing different products

• Use the same price basis: ex GST or inc GST, ex-port or delivered, bulk or bagged, same date.
• Divide by the real N%: our data lists 46% for granular urea and 20.2% for Gran-Am; see each product page for the published analysis and source.
• Remember products that carry other nutrients (sulphur, phosphorus) are doing more than supplying N; cost per kg N alone understates that.
• Do not forget spreading and freight, which are not in any figure on this page.

Does it pay?

A 1994 Western Australian bulletin describes a cost:price method, comparing the cost of a tonne of N on farm with the net grain price, and says the expected yield increase should cover fertiliser and application cost. Older prices in that bulletin are not used here. Our comparison tool includes a break-even calculator, and the nitrogen rate calculator shows cost per hectare and per kg of N.