About

Style guides (AP, Chicago, APA) require numbers to be spelled out in specific contexts. Manual conversion of large integers introduces transcription errors that compromise contracts, checks, and legal documents. This tool converts any integer with absolute value less than 1,000,000,000,000,000 (10¹⁵) into its standard English word form using recursive three-digit group decomposition. It handles zero, negative integers, and the full scale from ones through trillions. The algorithm mirrors the short-scale naming convention used in the United States, United Kingdom, and most English-speaking countries.

Limitations: this tool does not process decimal fractions, ordinal forms ("first", "second"), or currency formatting ("dollars and cents"). Input must be a whole integer. Numbers at or above one quadrillion (10¹⁵) are rejected to maintain naming-convention accuracy across regional standards.

Formulas

The conversion uses recursive three-digit group decomposition. An integer N is partitioned into groups of three digits from right to left. Each group G_k is assigned a scale label based on its position index k.

N = m∑k=0 G_k × 1000^k

where G_k ∈ [0, 999] and m = 4 (for up to trillions).

Scale labels by index k: k = 0 → (none), k = 1 → thousand, k = 2 → million, k = 3 → billion, k = 4 → trillion.

Each group G_k is decomposed further:

G_k = h × 100 + t × 10 + o

where h = hundreds digit, t = tens digit, o = ones digit. If t = 1, the teen value (t × 10 + o) is looked up as a single unit from a table of irregular names (eleven, twelve, thirteen, etc.). Otherwise tens and ones are looked up independently. If h > 0, the word for h is prepended with "hundred".

For negative input: the word "negative" is prepended to the result of converting the absolute value. For zero: the output is the literal string "zero".

Reference Data

Power of 10	Name	Digits	Example Integer	Word Form
10⁰	Ones	1	7	seven
10¹	Tens	2	42	forty-two
10²	Hundreds	3	315	three hundred fifteen
10³	Thousand	4 - 6	2,014	two thousand fourteen
10⁶	Million	7 - 9	5,000,100	five million one hundred
10⁹	Billion	10 - 12	1,000,000,000	one billion
10¹²	Trillion	13 - 15	8,500,000,000,000	eight trillion five hundred billion
10¹⁵	Quadrillion	16+	-	Not supported (exceeds limit)
Short-scale naming (US/UK standard)
0	Zero	1	0	zero
−1	Negative	Any	−58	negative fifty-eight
11 - 19	Teens (irregular)	2	13	thirteen
20,30,...90	Tens (regular)	2	80	eighty
100	Hundred	3	100	one hundred
101	Hundred + ones	3	101	one hundred one
110	Hundred + tens	3	110	one hundred ten
999	Max three-digit	3	999	nine hundred ninety-nine
10³ + teens	Thousand + teens	4 - 5	11,011	eleven thousand eleven
Mixed scales	All groups populated	15	123,456,789,012,345	one hundred twenty-three trillion four hundred fifty-six billion seven hundred eighty-nine million twelve thousand three hundred forty-five

Frequently Asked Questions

The tool uses the short-scale naming convention where each named group (thousand, million, billion, trillion) covers three additional digits. Supporting quadrillion (10¹⁵) and above would require extending the scale table, but more importantly, JavaScript's Number.MAX_SAFE_INTEGER is 9,007,199,254,740,991 (approximately 9 × 10¹⁵). To guarantee exact integer representation without floating-point artifacts, the tool caps input below 10¹⁵.

Short scale exclusively. In short scale, one billion equals 10⁹ (1,000,000,000). This is the standard in the United States, United Kingdom (since 1974), Canada, Australia, and most English-speaking countries. In the long scale (used in parts of continental Europe), one billion equals 10¹². If you need long-scale output, you must manually adjust the scale labels.

The omission of "and" follows American English convention. In American usage, "one hundred five" is standard. British English typically inserts "and" ('one hundred and five'). The AP Stylebook and Chicago Manual of Style do not mandate "and" in spelled-out numbers. This tool follows the no-'and' convention for consistency and brevity.

Yes. Prefix the integer with a minus sign. The output will begin with the word "negative" followed by the word form of the absolute value. For example, −42 converts to "negative forty-two". The negative sign must be the first character with no spaces before the digits.

The tool rejects it. Decimal fractions are not integers. The input validator checks that the value matches the pattern of an optional minus sign followed by one or more digits with no decimal point. If you need to convert the integer part of a decimal, truncate it yourself before entering (e.g., enter 3 instead of 3.14).

The algorithm always uses standard scale grouping. 1000 is "one thousand", never "ten hundred". Each three-digit group is processed independently with its corresponding scale label. The value 1100 becomes "one thousand one hundred", not "eleven hundred", because the algorithm decomposes into group G₁ = 1 (thousand) and G₀ = 100 (one hundred).