Convert Integers to Words
Spell out integers in English - supports billions, trillions, quadrillions with BigInt precision. Free, offline, client-side.
Spell out any integer in English - up to 999 quintillion (10²¹) with BigInt precision. Customize case, hyphenation, negative phrasing, and British-style "and". Batch-convert lists.
How to Use Convert Integers to Words
- Enter your integers - one per line, or separate them with commas, semicolons, or spaces. Negative numbers work (sign is preserved). The 200 ms debounce updates the output as you type.
- Pick a case format - lowercase for body text, UPPERCASE for emphasis, Title Case for headings, Sentence case for natural reading.
- Choose negative phrasing - "negative forty-two" is the formal default. "minus forty-two" matches mathematical convention. Either is correct English.
- Toggle hyphens - standard English hyphenates compound numbers (twenty-one, ninety-nine). Off gives "twenty one" - useful for informal writing or technical contexts.
- Toggle British "and" - UK English inserts "and" between the hundreds and the remainder (
one hundred and twenty-three). American English drops it. Both are widely accepted; pick the convention your audience uses. - Toggle show-both - outputs "42 = forty-two" pairs instead of just words. Useful for legal documents that require both forms ("the sum of $1,234 (one thousand two hundred thirty-four dollars)").
- Pick output separator - newline (default), comma (CSV-style), semicolon, or space. Switch instantly without re-typing.
- Copy or download - Copy puts the output on your clipboard; Download saves
integers-to-words.txt. Ctrl+Enter (⌘+Enter on Mac) forces a recompute. Stats line shows total count, word-length range, and any errors.
Frequently Asked Questions
What’s the maximum supported integer?
10²¹ − 1 = 999,999,999,999,999,999,999 (999 quintillion). Scales used: thousand (10³), million (10⁶), billion (10⁹), trillion (10¹²), quadrillion (10¹⁵), quintillion (10¹⁸). All arithmetic is BigInt-accurate; JavaScript’s regular Number type would silently round past 2^53 ≈ 9 × 10¹⁵.
Why use BigInt instead of regular Number?
JavaScript’s Number type is a 64-bit float. It can represent integers exactly only up to 2^53 – 1 = 9,007,199,254,740,991. Past that, precision degrades silently. 123456789012345678 + 1 returns 123456789012345680, not the correct result. BigInt avoids all that – every digit stays accurate up to our 10²¹ cap.
How are negative numbers handled?
Two phrasings: “negative forty-two” (formal default) or “minus forty-two” (mathematical). Both are standard English. The sign is detected on the input string, the absolute value is converted, and the prefix is prepended.
Should I use hyphens in compound numbers?
Standard English: yes. Numbers 21 through 99 (except multiples of 10) hyphenate: twenty-one, forty-five, ninety-nine. We hyphenate by default. Turn off for informal writing or when downstream tools require space-separated words.
What’s the British “and” option?
British English inserts “and” between the hundreds and the rest: “one hundred and twenty-three.” American English drops it. Both are widely understood; UK style is required for some British legal contexts and arithmetic-class conventions.
What’s the Title Case vs Sentence Case difference?
Title Case capitalizes every word (“Forty-Two”, “One Hundred Twenty-Three”) including the part after a hyphen. Sentence case only capitalizes the first letter of the first word (“Forty-two”). Title Case is for headings; Sentence case is for running text.
Can I use this for check writing?
Yes – that’s a primary use case. For US checks, use Sentence case with hyphens on. The output for $1,234.56 would be “One thousand two hundred thirty-four”. Most banks accept either US or UK convention; pick what matches your bank’s preference.
Is my data uploaded anywhere?
No. All conversion runs in your browser using BigInt arithmetic and string lookups. Open DevTools → Network and watch zero requests fire after the page loads. Safe for payroll numbers, financial documents, or anything private.
How fast is it?
A 100-line batch converts in under 50 ms on a modern laptop, even with trillion-sized numbers. The BigInt chunking is O(log₁₀₀₀ N) per number – bounded constant work for any practical input.
Does it work offline?
Yes. Total bundle is under 20 KB (HTML + CSS + JS, no external libraries). Once the page loads, disconnect and keep converting. Bookmark and use on flights, trains, or air-gapped machines.