Octal (base 8)
Octal (base 8) uses the digits 0 through 7. Each octal digit represents exactly three bits, which is why octal was widely used on early minicomputers and is still the conventional notation for Unix file-permission masks (e.g. 755).
Octal to Decimal Converter
755 (oct) = 493 (dec)
Convert octal numbers to decimal numbers exactly, for any size. Convertitive parses your input as a BigInt — so 64-bit values, 256-bit hex strings, and even larger numbers round-trip without rounding. For quick reference: 755 oct = 493 dec, and 100 oct = 64 dec.
Quick
How to convert octal numbers to decimal numbers
Enter a value
Type a octal integer in the From field. Allowed characters: 0 through 7.
Read the decimal result
The To field updates as you type. For example, the octal value 755 equals 493 in decimal.
Copy or share
Use the copy button to grab the result. You can change either base from its dropdown without leaving the page.
Reference table
Fifty representative values. Every row is computed exactly by the same BigInt-based converter that powers the widget above.
| Octal (oct) | Decimal (dec) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 5 |
| 6 | 6 |
| 7 | 7 |
| 10 | 8 |
| 11 | 9 |
| 12 | 10 |
| 13 | 11 |
| 14 | 12 |
| 15 | 13 |
| 16 | 14 |
| 17 | 15 |
| 20 | 16 |
| 21 | 17 |
| 22 | 18 |
| 23 | 19 |
| 24 | 20 |
| 30 | 24 |
| 37 | 31 |
| 40 | 32 |
| 44 | 36 |
| 52 | 42 |
| 60 | 48 |
| 62 | 50 |
| 77 | 63 |
| 100 | 64 |
| 144 | 100 |
| 177 | 127 |
| 200 | 128 |
| 310 | 200 |
| 377 | 255 |
| 400 | 256 |
| 764 | 500 |
| 777 | 511 |
| 1000 | 512 |
| 1750 | 1000 |
| 1777 | 1023 |
| 2000 | 1024 |
| 4000 | 2048 |
| 10000 | 4096 |
| 20000 | 8192 |
| 40000 | 16384 |
| 100000 | 32768 |
| 177777 | 65535 |
| 200000 | 65536 |
| 4000000 | 1048576 |
Frequently asked questions
- How do I convert octal numbers to decimal numbers?
- Enter your octal value above. Convertitive parses it as an arbitrary-precision integer and reformats it in decimal. The conversion is exact for any size — there's no float rounding.
- What is 755 in decimal?
- 755 (octal) equals 493 in decimal.
- Are negative numbers supported?
- Yes, with decimal. Two's-complement representations for fixed-width binary/hex are not supported here — the converter treats negative as a sign on the absolute value.
- What's the largest number I can convert?
- Any size. Convertitive uses JavaScript BigInt, which has no fixed upper bound — 256-bit hex strings, 512-bit and bigger all round-trip exactly.
- How many bits does the result take?
- An n-digit number in base 8 needs roughly 3.00 × n bits to store. The exact bit length equals ⌈log₂(value + 1)⌉.
- Is hex case-sensitive?
- Hexadecimal accepts letters in either case; this conversion doesn't involve hex.
- Are conversion factors exact?
- Yes. Base conversion is integer-to-integer; there are no factors, no rounding, no precision loss.
- Why would I convert octal numbers to decimal numbers?
- Decimal is the human-friendly form. Converting from octal to decimal makes a value easy to compare, communicate, or paste into spreadsheets and calculators.
About octal and decimal
Decimal (base 10)
Decimal (base 10) is the everyday number system, using the digits 0 through 9. It is the default base for almost all human-facing numbers — from prices to phone numbers to scientific measurements.