Convert Octal to Binary

Convert Octal (oct) to Binary (bin) instantly and accurately.

Selected Octal (oct) - available characters: 0, 1, 2, 3, 4, 5, 6, 7

Conversion Formula

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

Convert Octal (base 8) → Binary (base 2)

Step 1: Expand each digit of 52 (oct) by position:

        5 × 8^1 = 40
        2 × 8^0 =  2
        ────────────
        Sum = 42 (decimal)

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

        42 ÷ 2 = 21  r 0
        21 ÷ 2 = 10  r 1
        10 ÷ 2 =  5  r 0
         5 ÷ 2 =  2  r 1
         2 ÷ 2 =  1  r 0
         1 ÷ 2 =  0  r 1
        Read remainders upward: 101010

────────────────────────────
Result:  52 (oct) = 101010 (bin)

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.

About Binary

Binary (base 2) is the foundational numeral system of all digital electronics, using only 0 and 1. Each position represents a power of 2: 2⁰=1, 2¹=2, 2²=4, 2³=8. Leibniz formalised it in 1679; Shannon applied Boolean logic to circuits in 1948. 8 bits = 1 byte (256 values) - the fundamental unit in every CPU from the 8080 to ARM Cortex-X. Every integer, float, character, pixel, and instruction in any digital device is ultimately binary. Conversion: decimal 42 = 32+8+2 = 2⁵+2³+2¹ = 101010₂.

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