Transposing a number chart is not a procedure. There is nothing to move, nothing to rewrite, and no interval to count: the page already says 1, 4, 5, and a new key simply means those three digits resolve somewhere else. What a reader is actually doing, in the second between the count-off and the downbeat, is one lookup — and this is that lookup, printed.
Find the key down the left. Read across to the number the chart is asking for. The chord under your hands is in that cell. The row is the same seven notes a major scale would give you, which is the whole trick: the notation borrowed the scale everybody already knows and then refused to name any of it.
| Key | 1 major | 2 minor | 3 minor | 4 major | 5 major | 6 minor | 7 diminished |
|---|---|---|---|---|---|---|---|
| A | A | B | C# | D | E | F# | G# |
| A# | A# | C | D | D# | F | G | A |
| B | B | C# | D# | E | F# | G# | A# |
| C | C | D | E | F | G | A | B |
| C# | C# | D# | F | F# | G# | A# | C |
| D | D | E | F# | G | A | B | C# |
| D# | D# | F | G | G# | A# | C | D |
| E | E | F# | G# | A | B | C# | D# |
| F | F | G | A | A# | C | D | E |
| F# | F# | G# | A# | B | C# | D# | F |
| G | G | A | B | C | D | E | F# |
| G# | G# | A# | C | C# | D# | F | G |
Why four of the seven columns carry a warning
The second line in each column head is the same in every row, and that is the fact worth carrying around: the key's own scale gives a major chord on the 1, 4 and 5, a minor on the 2, 3 and 6, and a diminished chord on the 7. Every key. No exceptions. So the pattern is memorised once and never looked up again.
It matters because a bare number on a chart is a MAJOR chord regardless. On the 1, 4 and 5 that agrees with the key and nothing needs saying. On the 2, 3 and 6 it does not agree, which means a bare 2 is a deliberate act — the writer wanted the major chord the key would not have supplied — and a chart that wanted the ordinary minor had to write 2-. Four columns of this grid are places where the notation and the key signature can disagree, and being fluent is mostly being unsurprised by them.
The 7 is the odd one out for a different reason: almost no chart asks for it. A diminished triad is rare enough on a session floor that when the digit does appear it is usually carrying a mark, and it is worth a second look rather than a reflex.
What this looks like at a count-off
Nobody reads this grid live. What happens is that a key gets called, the reader fixes the 1, and the other six positions arrive relative to it — the 4 and the 5 first, because they carry most of the repertoire, and the rest as they come up. Ten minutes with the drill in an unfamiliar key does more for that than an hour with this table, which is why the table is here for checking and the drill is here for learning.