Pepfrag can calculate:
1) the molecular weight (MW) of the peptide
2) the m/z value of the [M+H]+ ion of the peptide
3) the m/z value of the common fragment ions (a,b,c,x,y,z) observed during MS/MS of the peptide

Fragment ions can be sorted by mass or by ion type (in ascending or descending order).

An auto-fill option is available for entering common peptide sequences.