You can use the form below to determine the most appropriate string to use for your dulcimer. Well actually this will work for any stringed instrument that uses typical steel wire. The calculations are based on a string tension of 13.8 pounds-force and a string density value of 0.283 pounds-mass per cubic inch.  The density of wound strings will be slightly different but close enough for the purpose of selecting the gauge.

You need to know the length between the nut and bridge. Then you need to know the open tuning for the string, e.g. A below middle C on the piano keyboard.

Enter string length:   inches.

Select open-string tuning for string to be replaced (typical tuning is D A d): d' c#' c' (octave above middle c) b a# a g# g f# f e d# d c# c (middle c) B A# A G# G F# F E D# D C# C (octave below middle c) B' A'# A' G'# G' E' D'# D'

Note: Any size above 0.018" may require a wire-wound string. Elixir wire-wound squeakless are desirable.