๐ข Base36 Converter
Convert between decimal numbers and Base36 (a numeral system using the 36 characters 0-9 and a-z). Commonly used for short URLs and compact unique IDs.
How to use
- Choose "decimal to Base36" or "Base36 to decimal" mode.
- Enter the value to convert.
- The converted value is shown automatically.
How the calculation works
Base36 represents numbers with 36 symbols: the digits 0โ9 and the letters aโz. It writes large numbers in fewer digits than decimal and uses only letters and digits, which suits URLs and short IDs. Decimal to base 36: repeatedly divide by 36 and turn each remainder into 0โ9 or aโz, from the lowest digit up. Base 36 to decimal: from the highest digit down, compute "value so far ร 36 + this digit". The tool uses JavaScript BigInt (arbitrary-size integers), so numbers beyond 2โตยณ (about 9 quadrillion) convert exactly. Upper and lower case are treated the same.
Worked example
12345 โ 9ix 9 ร 36ยฒ + 18 ร 36 + 33 = 11,664 + 648 + 33 = 12,345 (9 = 9, i = 18, x = 33) zzzzzzzzzzzz (12 digits) โ 4,738,381,338,321,616,895 (36ยนยฒ โ 1, too large for ordinary JavaScript numbers to hold exactly)
Things to be aware of
- Base 36 needs about 1/1.55 as many digits as decimal for the same number.
- It includes easily confused characters such as 0/o and 1/l, so IDs people type by hand are sometimes better in a format that excludes them, such as Crockford Base32.
- Fractions and negative numbers are not supported.
FAQ
What is Base36?
A base-36 numeral system combining the digits 0-9 with the letters a-z, letting you represent large numbers with fewer characters than decimal.
What is it used for?
Itโs commonly used for URL shorteners and database ID generation, wherever you want to represent a number as compactly as possible.
Does case matter?
No โ Base36 input is case-insensitive and treated the same either way.