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Increment letters (Rev A -> Rev B) and wrap A–Z shifts with CODE & CHAR
Step engineering revision letters forward ("A" -> "B"), wrap "Z" cleanly back to "A" with MOD(..., 26), and apply symmetric ROT13 character shifts.
Zero-base uppercase ASCII at 65 ("A") so MOD(..., 26) wraps cleanly!
In ASCII, uppercase "A" through "Z" occupy codes 65 through 90. Simply writing CHAR(CODE(A2) + 1) turns "A" into "B"—but turns "Z" (90 + 1 = 91) into "["!
Subtracting 65 first (CODE(UPPER(A2)) - 65 -> 0..25), adding your shift k inside MOD(..., 26), and adding 65 back inside CHAR(...) wraps "Z" + 1 -> "A" cleanly, and makes k = 13 a self-inverting ROT13 cipher (applying k = 13 twice restores the original letter)!
This example operates on one ASCII letter A–Z, not an entire text string. UPPER normalizes lowercase input. Use an integer shift. These codes are the portable ASCII subset; CODE/CHAR behavior for other characters can differ by platform.
ROT13 is reversible obfuscation, not encryption or protection for confidential data. The illustrative revision-label formula assumes exactly "Rev " followed by one uppercase A–Z letter; real revision schemes may skip letters or continue as AA instead of wrapping.
| Input Letter | Shift +1 (Next Rev) | Shift +13 (ROT13) | Double ROT13 (+13 again) |
|---|---|---|---|
| "A" (ASCII 65) | "B" | "N" | "A" (Restored!) |
| "C" (ASCII 67) | "D" | "P" | "C" |
| "Z" (ASCII 90) | "A" (Wraparound!) | "M" | "Z" |
Wraparound letter-shift and engineering revision-step formulas
Works for positive shifts (+1, +13) AND negative shifts (-1 steps "A" backward to "Z" because Excel/Arte MOD(-1, 26) = 25!).
=IFERROR(IF(AND(LEN(A2)=1,CODE(UPPER(A2))>=65,CODE(UPPER(A2))<=90,ISNUMBER(B2),B2=INT(B2)),CHAR(MOD(CODE(UPPER(A2)) - 65 + B2, 26) + 65),"Use one A-Z letter and an integer shift"),"Use one A-Z letter and an integer shift")Advance an engineering drawing label ("Rev A" -> "Rev B")
Extracts the trailing revision letter with RIGHT(C2, 1) and increments it.
="Rev " & CHAR(MOD(CODE(RIGHT(C2, 1)) - 65 + 1, 26) + 65)Try the example
Use the original values or change them to test your understanding.