B#dim is a diminished, spelled B#, D# and F#. In Ukulele (low G) tuning (G3 C4 E4 A4) the easiest shape is x323, which sits at fret 2, spans 1 fret and mutes 1 string. 12 positions for it are shown below, from the nut up to fret 14.
Notes and intervals
Note
B#
D#
F#
Interval
1P
3m
5d
12 ways to play it
Ordered by how hard they are to fret, easiest first, one per position on the neck. Fret numbers are relative to the position marked beside each grid.
x323sits at fret 2, spans 1 fret and mutes 1 string5686sits at fret 5 and spans 3 fretsx0119sits at fret 9, spans 2 frets, lets 1 string ring open and mutes 1 stringx086sits at fret 6, spans 2 frets, lets 1 string ring open and mutes 1 string8089sits at fret 8, spans 1 fret and lets 1 string ring open11011xsits at fret 11, needs no stretch at all, lets 1 string ring open and mutes 1 stringx151415sits at fret 14, spans 1 fret and mutes 1 string5323sits at fret 2 and spans 3 frets532xsits at fret 2, spans 3 frets and mutes 1 string5026sits at fret 2, spans 4 frets and lets 1 string ring open5086sits at fret 5, spans 3 frets and lets 1 string ring open8686sits at fret 6 and needs a barre across 3 strings at fret 6
Keys B#dim belongs to
B#dim is diatonic to 8 of the 96 keys this app knows, playing a different role in each.