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The Kjeldahl method is used to determine the nitrogen content in organic and inorganic samples.For longer than 100 years the Kjeldahl method has been used for the determination of nitrogen in a wide range of samples. The determination of Kjeldahl nitrogen is made in foods and drinks, meat, feeds, cereals and forages for the calculation of the protein content. Also the Kjeldahl method is used for the nitrogen determination in wastewaters, soils and other samples.

The calculations for % nitrogen or % protein must take into account which type of receiving solution was used and any dilution factors used during the distillation process. In the equations below, “N” represents normality. “ml blank” refers to the millilitres of base needed to back titrate a reagent blank if standard acid is the receiving solution, or refers to millilitres of standard acid needed to titrate a reagent blank if boric acid is the receiving solution.

This calculator calculates the nitrogen percentage (%) using normality, base of standard acid, weight of sample values.