🌐 Language
English uses short scale (109 = billion); Spanish uses long scale (1012 = billón). See the SEO content above for full details.
🔢 Number
BigInt-safe: paste a 30-digit number if you need to. Decimals, hex literals, and scientific notation are rejected.
📤 In words
🔁 Normalized input
The exact integer the converter saw, after stripping leading zeros and whitespace.
ℹ️ About Number to Words Converter
Spell integers in English or Spanish words
Paste or type any integer — positive, negative, or zero — and the tool spells it out as words
in either English (American/modern British short scale) or Spanish (Real Academia Española long
scale). Range: magnitudes strictly less than 1036 are accepted, so
you can spell any value through the decillion range (1033) in English. Anything
larger raises a validation error rather than silently truncating.
Input arrives as either a JavaScript number or a digit string. Digit strings let you spell
BigInt-safe values like
123,456,789,012,345,678,901,234,567,890 without worrying about IEEE-754 precision.
⚠️ Short scale vs long scale — they disagree!
The single most important thing to know about this tool: English and Spanish use different naming systems for large numbers. A "billion" in English does not translate as "billón" in Spanish. This is a real-world translation hazard that this tool handles automatically — each language follows its own canonical convention.
| Power of 10 | English (SHORT scale) | Spanish (LONG scale) |
|---|---|---|
| 106 | one million | un millón |
| 109 | one billion | mil millones (NOT billón) |
| 1012 | one trillion | un billón |
| 1015 | one quadrillion | mil billones |
| 1018 | one quintillion | un trillón |
| 1024 | one septillion | un cuatrillón |
| 1030 | one nonillion | un quintillón |
| 1033 | one decillion (just over our cap) | mil quintillones |
Short scale (used by modern English, Brazilian Portuguese, and most English-influenced styles): each new "-illion" is 1,000 times the previous one. Long scale (used by most European Romance and Germanic languages, including Spanish, French, and German): each new "-illón" is 1,000,000 times the previous one, with an intermediate "mil X" level between each. So 109 is "billion" in short scale but "mil millones" (literally "one thousand millions") in long scale.
English rules (short scale)
- Compound numbers from 21 to 99 are hyphenated:
twenty-one,forty-five,ninety-nine. - "and" is omitted in the modern American convention:
one hundred one, notone hundred and one. - Scale words don't pluralise:
two million, nottwo millions. - Negatives are prefixed with
negative:-42→negative forty-two. - Zero is
zero.
Spanish rules (long scale)
- 21–29 collapse to one word:
veintiuno,veintidós, …veintinueve(NOT "veinte y uno"). - 31–99 use "y":
cuarenta y cinco,sesenta y dos,noventa y nueve. No hyphens. - "cien" / "ciento": exactly 100 is
cien; 101–199 useciento(e.g.ciento uno). - "mil" is unmarked: 1,000 is
mil— never "un mil". 2,000 isdos mil. - Pluralisation rule for "-illón" levels: 1×106 is
un millón, 2×106 isdos millones(add-esto "millón" → "millones"). Same pattern at billón → billones, trillón → trillones, etc. - Apocopation of "uno": "uno" becomes
unbefore a masculine noun.veintiún mil,treinta y un millones. - Negatives are prefixed with
menos:-42→menos cuarenta y dos. - Zero is
cero.
Worked examples
| Number | English (short scale) | Spanish (long scale) |
|---|---|---|
| 0 | zero | cero |
| 21 | twenty-one | veintiuno |
| 45 | forty-five | cuarenta y cinco |
| 100 | one hundred | cien |
| 101 | one hundred one | ciento uno |
| 1,000 | one thousand | mil |
| 12,345 | twelve thousand three hundred forty-five | doce mil trescientos cuarenta y cinco |
| 1,000,000 | one million | un millón |
| 1,000,000,000 | one billion | mil millones |
| 1,000,000,000,000 | one trillion | un billón |
| -42 | negative forty-two | menos cuarenta y dos |
Use cases
- Cheque/legal documents: spell out monetary amounts in both digits and words to prevent forgery.
- Accessibility: generate screen-reader-friendly text for large numeric values.
- Translation tooling: render currency or quantity values in localised long-form for receipts and invoices.
- Math/language education: teach the difference between short and long scale numbering systems.
- Test data: generate human-readable labels for synthetic data sets.
Limits and errors
- Maximum absolute magnitude is
1036 − 1(a 36-digit number of all 9s). Larger values raise "value magnitude exceeds 10^36 − 1". This keeps every result inside named scales — the top English scale reached is "decillion" (1033). - Non-integer input (e.g.
12.5,0.1, hex, scientific notation strings) is rejected. - Unsupported language values (anything other than
"en"or"es") raise "language must be \"en\" or \"es\"". - The browser and API share the same TypeScript module, so both paths produce identical output.
References
- Long and short scales (Wikipedia) — comprehensive comparison of the two numbering conventions and which languages use which.
- Names of large numbers (Wikipedia) — million, billion, trillion, etc. through decillion and beyond.
- Real Academia Española — "billón" — official Spanish definition (1012, NOT 109).
- Real Academia Española — cardinal numbers — official Spanish spelling rules for cardinals.
API Usage Example:
POST /api/tools/math/number-to-words
Content-Type: application/json
{
"value": "1000000000",
"language": "en"
}