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Decimal to Octal Number System Conversion

In this tutorial, we will learn about the conversion of decimal to octal number systems with the help of examples. By Saurabh Gupta Last updated : May 10, 2023

Decimal to Octal Number System Conversion

Converting a number from Decimal to Octal is almost similar to converting Decimal into Binary, although just one difference is that unlike Binary conversion, here in an integral part, we successively divide the number by 8 until the quotient is 0 (the last remainder becomes the MSB). The remainders read from bottom to top give the equivalent octal integer number. and in the fractional part, we multiply it by 8 till the fractional part of the product is 0. The first integer in the product term gives the MSB, thus the integers read from top to bottom gives the equivalent octal fraction.

Same as in decimal to binary conversion, to convert a mixed decimal number into octal, we first separate the integral and the fractional part and then convert them into octal individually, after converting both to octal separately, we combine them back together to get the desired result.

Decimal to Octal Number System Conversion: Example 1

Convert (73.625)₁₀ to ( ? )₈

Solution

Firstly, we will separate the integral part (73)₈ and the fractional part (0.625)₈. Now, we will convert each of them to octal individually.

Integral Part

Divisor	Quotient	Remainder
8	73
8	9	1 LSB
8	1	1
8	0	1 MSB

All the remainders read from top to bottom, where topmost is the LSB and bottom one is the MSB.

Therefore, (73)₁₀ = (111)₈

Fractional Part

    0.625 * 8 = 5.000

The integer part of the product term read from top to bottom forms the equivalent octal number i.e., (.625)₁₀ = (0.5)₈

After converting both integral part and fractional part individually into octal, now we combine both to get our desired result i.e., (73.625)₁₀ = (111.5)₈

Decimal to Octal Number System Conversion: Example 2

Convert (965.198)₁₀ to ( ? )₈

Solution

Integral Part

Divisor	Quotient	Remainder
8	965
8	120	5 LSB
8	15	0
8	1	7
8	0	1 MSB

The remainders read from bottom to top gives the equivalent octal number i.e., (965)₁₀ = (1705)₈.

Fractional Part

    0.198 * 8 = 1.584	MSB
    0.584 * 8 = 4.672
    0.672 * 8 = 5.376
    0.376 * 8 = 3.008
    0.008 * 8 = 0.064
    0.064 * 8 = 0.512	LSB

The integer part of the product term read from top to bottom forms the equivalent octal number i.e., (0.198)₁₀ = (0.145300)₈.

After converting both integral part and fractional part individually into octal, now we combine both to get our desired result i.e., (965.198)₁₀ = (1705.145300)₈

Decimal to Octal Number System Conversion: Example 3

Convert (296.225)₁₀ to ( ? )₈

Solution

Integral Part

Divisor	Quotient	Remainder
8	296
8	37	0 LSB
8	4	5
8	0	4 MSB

The remainders read from bottom to top gives the equivalent octal number i.e., (296)₁₀ = (450)₈.

Fractional Part

    0.225 * 8 = 1.80    MSB
    0.80  * 8 = 0.64
    0.64  * 8 = 5.12
    0.12  * 8 = 0.96
    0.96  * 8 = 7.68     LSB

The integer part of the product term read from top to bottom forms the equivalent octal number i.e., (0.198)¹⁰ = (0.10507)⁸.

After converting both integral part and fractional part individually into octal, now we combine both to get our desired result i.e., (296.225)₁₀ = (450.10507)₈.

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