Convert Base 9 to Octal

Convert Base 9 (base 9) to Octal (oct) instantly and accurately.

Selected Base 9 (base 9) - available characters: 0, 1, 2, 3, 4, 5, 6, 7, 8

Conversion Formula

Step-by-step example using the value 42 (decimal):

Convert Base 9 (base 9) → Octal (base 8)

Step 1: Expand each digit of 46 (base 9) by position:

        4 × 9^1 = 36
        6 × 9^0 =  6
        ────────────
        Sum = 42 (decimal)

Step 2: Divide 42 by 8 repeatedly (read remainders upward):

        42 ÷ 8 = 5  r 2
         5 ÷ 8 = 0  r 5
        Read remainders upward: 52

────────────────────────────
Result:  46 (base 9) = 52 (oct)

About Base 9

Nonary (base 9) uses digits 0-8. Each position is a power of 9: 9⁰=1, 9¹=9, 9²=81. Because 9 = 3², each nonary digit maps to exactly 2 ternary digits (0=00 … 8=22). The finite field GF(9) = GF(3²) is used in certain error-correcting codes and algebraic geometry. The 3×3 magic square sums to 15 in every row/column/diagonal and is deeply tied to mod-9 arithmetic. Conversion: decimal 42 = 4×9+6 = 46₉.

About Octal

Octal (base 8) uses digits 0-7. Each position is a power of 8: 8⁰=1, 8¹=8, 8²=64. Because 8 = 2³, each octal digit = exactly 3 binary bits. The Unix/Linux file permission system (chmod 755 = rwxr-xr-x; 7=111, 5=101) uses octal for concise 3-bit rwx triplets. The DEC PDP series encoded 12- and 16-bit words naturally in octal. In C/C++/JS a leading zero denotes octal: 0755 = 493₁₀. Conversion: decimal 42 = 5×8+2 = 52₈.

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