This Peptide Chemical Calculator application is a tool to calculate the molecular formulae, accurate mono isotopic and average masses of your peptide. You can work with a sequence in one- or three-letter amino acid code, choose few popular modifications on N- and C-terminals or add disulfide bridges. The masses are calculated using the following atomic weights: H Element Monoisotopic mass - 1.0078250 Average mass - 1.0079400 C Element Monoisotopic mass - 12.0000000 Average mass - 12.0110000 N Element Monoisotopic mass - 14.0030740 Average mass - 14.0067400 O Element Monoisotopic mass - 15.9949146 Average mass - 15.9994000 F Element Monoisotopic mass - 18.9984033 Average mass - 18.9984000 P Element Monoisotopic mass - 30.9737634 Average mass - 30.9737600 S Element Monoisotopic mass - 31.9720718 Average mass - 32.0660000 Cl Element Monoisotopic mass - 34.9688527 Average mass - 35.4527000 Br Element Monoisotopic mass - 78.9183361 Average mass - 79.9040000