Ammonia toxicity calculator
Freshwater estimate, with no salinity correction. Confirm the test kit’s reporting units and follow product or veterinary guidance before treatment.
Ammonia method and limits
T is temperature in Celsius. This uses the Emerson equation with a 2729.92 constant, reported in secondary sources. This calculator accepts 0 to 50°C (32 to 122°F) and pH 4 to 11.
NH3 and NH3-N reporting units differ by a factor of 1.216. Check the kit’s manual. Results are expressed as mg/L NH3-N.
The bands indicate no acute concern below 0.05 mg/L, chronic stress from 0.05 to 0.4 mg/L, and urgent action above 0.4 mg/L. Published acute toxicity figures for carp and goldfish vary, with a range starting around 0.9 mg/L. Exposure time and species affect risk.
pH can rise during the afternoon. Test nitrite too, and check replacement water for ammonia if it contains chloramine. Salt can lower the free-ammonia fraction; this calculation does not correct for it.
For a high reading, use a partial water change, stop feeding and add aeration. Dechlorinate and temperature-match replacement water. Avoid rapid pH changes.