Mel Wilson's Chord Dictionary

TRANSPOSITION CHART
transposition chart
The Transposition Chart is made up of the chromatic scale arranged in rows and columns.

To transpose from one key to another:
Locate the row that starts with the letter name of the key the song is in.
To find the letter name of the chord in the new key, simply read across from the original key to the new key.

Remember:
When transposing chords of a song from one key to another the only thing that changes is the letter name of the chord. For instance changing a Cmaj7 to Gmaj7 only changes the letter name of the chord.The chord type (in this case the maj7 part of the chord name) doesn't change.

Examples:
Let's use the chord progression Cmaj7, Am7, Dm7-5, G9, Cmaj11 which is in the key of C, and transpose it to the key of G. C is the forth row down on the chart. G is three up from the bottom of the chart. The first chord to change is the Cmaj7. The C in the forth row matches with G in the third row up from the bottom, so the Cmaj7 becomes Gmaj7. The A in the forth row matches with E in the the third row up from the bottom, so the Am7 becomes an Em7. Likewise Dm7-5 becomes Am7-5, G9 becomes D9, and Cmaj11 becomes Gmaj11.

Let's transpose the same chord progression from the key of C to the key of Eflat.
Eflat is the 7th row down. Notice that this cell in the chart has a sharp sign () and a flat sign () in it. That is because it represents Dsharp or Eflat. On a piano this would be the black key above D or below E. The C in our chord progression matches the Eflat in the seventh row, so Cmaj7 becomes Eflatmaj7, Am7 becomes Cm7, Dm7-5 becomes Fm7-5, G9 becomes Bflat9, and Cmaj11 becomes Eflatmaj11.

to melmusic.com