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Octal to Decimal Converter
Convert octal integers to exact decimal integers in your browser with explicit ASCII, Unicode code point, and UTF-8 byte handling.
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Convert octal integers to exact decimal integers
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Detailed conversion guide
How to Convert Octal to Decimal
Octal is base 8. Each position is a power of eight: 755 equals 7×64 + 5×8 + 5, producing decimal 493.
The converter uses BigInt rather than floating-point Number arithmetic, so long permission masks, packed values, and test vectors remain exact.
| Input | Output | Meaning |
|---|---|---|
10 | 8 | one power of eight |
17 | 15 | two digits |
177 | 127 | ASCII boundary |
755 | 493 | Unix permission form |
Octal to Decimal with BigInt
Validate digits 0-7, normalize an optional 0o prefix, then construct a BigInt and call toString(10). Never accept 8 or 9 as partial input.
// validate first, then convert
const value = Number.parseInt(token, radix);
if (!Number.isInteger(value)) throw new Error("Invalid input");Octal Digits, Prefixes, and Large Values
A leading zero alone is not treated as an implicit language-specific octal marker. Use 0o when you want an explicit prefix.
Digits 8 and 9, negative signs, fractions, and prose are unsupported. Invalid input produces no partial decimal result.
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