Urea vs ammonium nitrate: cost per kilogram of nitrogen
A tonne of granular urea nearly always costs more than a tonne of ammonium nitrate, and it is nearly always the cheaper way to buy nitrogen. Both things are true, because the tonne is the wrong unit. This guide shows the only comparison that matters: pounds per kilogram of nitrogen, and what the headline saving does not include.
The arithmetic
Granular urea is 46% nitrogen: a tonne carries 460 kg of N. UK ammonium nitrate is 34.5% nitrogen: a tonne carries 345 kg. Divide each price per tonne by its kilograms of nitrogen and you get the true cost of the nutrient. Urea at 400 pounds per tonne is 0.87 pounds per kg N; AN at 350 pounds per tonne is 1.01 pounds per kg N. The dearer tonne is the cheaper nitrogen.
The break-even is fixed by the analysis: urea is the cheaper kilogram of nitrogen whenever its price per tonne is below 1.33 times the AN price. Above that ratio, AN wins on cost.
What the headline saving leaves out
Urea's nitrogen is not plant-ready. It must convert in the soil first, and during conversion some nitrogen can be lost to the air as ammonia, especially when urea is spread onto a warm, dry surface and no rain follows. Losses vary widely with weather and soil; the saving per kilogram bought is not the saving per kilogram the crop actually receives.
Regulation reflects this. In England, solid urea is subject to spreading restrictions under industry schemes: unprotected urea is for early-season use, and later applications are expected to use a urease inhibitor, which adds cost per tonne and narrows the gap to AN. Factor the inhibitor into your comparison if your window runs past early spring.
AN's nitrogen is half nitrate, available to the crop immediately and more predictable in cool conditions, which is why much of the UK trade still prices everything against it.
Live comparison: pounds per kilogram of nitrogen
Computed from today's index estimates. AN carries 34.5% N, granular urea 46% N.
The tiles below divide today's index estimates by each grade's nitrogen content. Both underlying figures are daily estimates produced from driver indices and validated against weekly UK market prints; follow the grade pages for the full picture including the uncertainty band.
Live comparison: pounds per kilogram of nitrogen
Computed from today's index estimates. AN carries 34.5% N, granular urea 46% N.
Live comparison is loading or temporarily unavailable. The arithmetic in this guide still applies: divide each price per tonne by its kilograms of nitrogen per tonne.
AI-forecasted market estimates, getting sharper as farmers add what they paid. Indicative, not a transactable quote.