Base-8 number system using digits 0–7. Often used in computing and file permissions.

Can I convert negative numbers?

This tool converts non-negative integers only; negative input is treated as invalid.

Only whole numbers are supported; fractional parts are not converted.

Online Decimal to Octal Converter

Convert a decimal integer to octal (base 8).

Decimal number

What is octal?: Base-8 number system using digits 0–7. Often used in computing and file permissions.
Can I convert negative numbers?: This tool converts non-negative integers only; negative input is treated as invalid.
What about decimals?: Only whole numbers are supported; fractional parts are not converted.

Celsius to Fahrenheit Converter

Convert Celsius to Fahrenheit and Fahrenheit to Celsius instantly. Free temperature converter.

Tip Calculator

Calculate tip and split the bill. Enter bill amount, tip percentage, and number of people.

Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals to numbers. Supports 1–3999.

Combinations Calculator

Calculate C(n,r) — the number of ways to choose r items from n without order. Uses n!/(r!(n-r)!).

Combinations with Replacement Calculator

Calculate the number of ways to choose r items from n with repetition allowed. Formula: C(n+r-1, r).

Even Permutations Calculator

Count how many permutations of n objects are even (expressible as an even number of swaps). For n ≥ 2, equals n!/2.