What This Tool Does
This tool formats a number using the browser's built-in Intl.NumberFormat API, letting you preview exactly how a value will render as a decimal, currency, percentage, or unit, in any locale, before writing a single line of code. Every option maps directly to a real Intl.NumberFormat setting.
How to Format a Number
Type a number into the input, then choose a style, decimal, currency, percent, or unit, and a notation, standard, compact, scientific, or engineering. The formatted result updates instantly, along with a comparison table showing the same number across 10 locales and a code snippet you can copy directly into your project.
Notation Styles: Compact, Scientific, and Engineering
Standard notation writes out the full number with grouping separators, like 1,234,567. Compact notation abbreviates large numbers, like 1.2M, with a short or long display option. Scientific notation writes the number as a coefficient times a power of ten, and engineering notation does the same but restricts the exponent to multiples of three, matching how engineers commonly express magnitude.
Comparing Locales
The same number and formatting options can look very different across locales, decimal and thousands separators swap in many European locales, currency symbols and their position vary, and some locales use entirely different digit or grouping conventions. The locale comparison table applies your exact settings across 10 common locales at once, click any row to switch the primary locale to it.
Common Uses for a Number Formatter
Previewing how a price or currency value will display before implementing it, checking that a percentage or large number reads correctly in a specific locale, and generating a correct Intl.NumberFormat call without looking up its option names from documentation are all common uses for this tool. Use it as an intl numberformat online preview, a way to format number with commas or as a thousands separator formatter, a currency formatter online, a compact number notation and scientific notation converter, a locale number formatting comparison, a javascript number format tool, and a number formatter with units for kilometers, kilograms, or bytes.