Where to capo for F Dorian
Put the capo at fret 3 and play F Dorian using D Dorian shapes. That is the easiest of the eight positions ranked below, and it is what most players reach for. Against playing F Dorian open, it drops the mean difficulty of the key's seven chords from 5.6 to 3.4 and gains 15 ringing open strings.
You want F. Capo 3 and play in D.
All eight positions, ranked
Each row transposes F Dorian down by that many frets to find the shapes your hand would actually make, then scores the best voicing of all seven chords — fewer fingers, less stretch, closer to the nut, fewer muted strings. Lower is easier. Standard tuning (E2 A2 D3 G3 B3 E4).
What you are playing
The seven chords of F Dorian are Fm, Gm, Ab, Bb, Cm, Ddim, Eb — the ones the ranking above is scored against. Their diagrams are on the F Dorian key page.