Number ↔ Words Converter

How to Use the Number ↔ Words Converter

This tool converts between numeric digits and written English number words in both directions. You can spell out an integer such as 572 as “five hundred seventy-two,” or parse a phrase like “seven thousand five hundred” back into 7500. Everything runs in your browser, so no data is sent to a server.

• Number → words: Enter a whole number between 0 and 999,999,999 in the first field to see its English wording in the “Words result” area.
• Words → number: Type standard English number words in the third field (for example, “one hundred twenty-three” or “two thousand and six”) to see the digits in the “Number result” field.

The converter is designed for clarity and consistency, making it useful for check writing, invoices, educational practice, and accessibility scenarios such as screen readers.

How Number to Words Conversion Works

At the core of the tool is the idea of place value: every digit in a number represents a multiple of a power of ten. Any non-negative integer can be written as a sum of digits times powers of ten. In MathML, positional notation can be expressed as:

Here, each di is a digit from 0 to 9. The script takes those digits in groups of three (hundreds, tens, ones) and associates each group with an English “scale word” such as thousand or million.

Core Word Mappings

The converter uses a small dictionary of fixed words that cover the basic numbers. Larger values are constructed from these building blocks.

Chunking into Hundreds, Thousands, and Millions

To spell a number, the script splits it into three-digit chunks from right to left:

• 0–999: units (no scale word)
• 1,000–999,999: thousands
• 1,000,000–999,999,999: millions

Each chunk is processed with a helper function that:

1. Emits a “hundreds” part if the first digit is non-zero (for example, 5 in 572 becomes “five hundred”).
2. Looks at the last two digits; if they are 0–19, it uses a direct mapping such as “twelve” or “nineteen.”
3. For 20–99, it combines a tens word like “twenty” or “sixty” with a ones word, using a hyphen when required, for example “twenty-three.”

The final result is assembled by attaching scale words to each non-zero chunk and joining them with spaces.

How Words to Number Parsing Works

Parsing in the reverse direction starts with a phrase of English number words and produces a single integer. The parser:

• Normalizes the text by converting it to lowercase and removing commas and other punctuation.
• Splits the phrase into tokens such as ["two", "thousand", "and", "six"].
• Maintains a running accumulator for the current group and a total for the whole number.

Small number words like “one,” “eleven,” or “ninety” add their value into the accumulator. Magnitude words such as “hundred,” “thousand,” and “million” scale or move that accumulator:

• Hundred: multiplies the current accumulator by 100.
• Thousand or million: multiplies the current accumulator by the magnitude and adds it to the running total, then resets the accumulator for the next group.

Consider “two thousand and six”:

1. two sets the accumulator to 2.
2. thousand multiplies 2 by 1000 to get 2000 and adds it to the total.
3. and is treated as optional and ignored.
4. six sets the accumulator to 6; at the end, this is added to the total for a result of 2006.

The same approach allows the parser to handle “seven hundred eighty-nine thousand three hundred one,” “one hundred twenty-three,” and similar standard cardinal phrases.

Worked Examples

Number → Words

• 42 → “forty-two”
• 1,005 → “one thousand five”
• 572 → “five hundred seventy-two”
• 999,999,999 → “nine hundred ninety-nine million nine hundred ninety-nine thousand nine hundred ninety-nine”

Words → Number

• “seven thousand five hundred” → 7500
• “two thousand and six” → 2006
• “one hundred twenty-three” → 123
• “one hundred and one” (with “and”) → 101

Both “one hundred one” and “one hundred and one” are interpreted as the same value. The parser is tolerant of optional “and” in typical British-style wording while producing a consistent spelling style in its own output.

Interpreting the Results

When you use the converter, keep the following points in mind as you interpret the output:

• The Words result field is the tool’s preferred, consistent spelling for the number you entered. It uses the short scale (thousand, million, billion) and standard cardinal forms.
• The Number result field shows a plain integer with no commas. You can copy it directly into spreadsheets, forms, or code.
• Hyphens are used for compound tens like “twenty-one,” but the parser will usually accept input with or without hyphens.
• Optional “and” is accepted in phrases such as “one hundred and twenty-three,” but the generated output may omit “and” for consistency.

These conventions are designed to keep the results predictable while still understanding the most common variants people type.

Comparison of Supported and Unsupported Inputs

Supported Range, Language, and Limitations

To avoid confusion, the tool follows a clearly defined scope:

• Range: Non-negative integers from 0 up to 999,999,999, matching the limits of the numeric input field.
• Language: English, short scale (thousand, million, billion). This coverage is suitable for both US and UK usage for cardinal numbers.
• Style: The generated wording is a neutral, compact style like “one hundred one” rather than “one hundred and one,” though both forms are understood when parsing.

The following constraints are important:

• No negatives: Negative numbers such as −1 are not supported. If you need them, you can manually add “minus” to the spelled-out form.
• No decimals or fractions: Inputs such as 3.5 or “three and a half” are out of scope. Convert such values to whole numbers first if appropriate.
• No currencies or units: Phrases including words like “dollars,” “euros,” or “percent” are not parsed. Use plain numbers only.
• No ordinals: Terms like “first,” “second,” or “twenty-first” are not handled; convert them manually into cardinals (for example, “one,” “two,” “twenty-one”) before using the tool.
• Standard wording only: Highly informal, abbreviated, or ambiguous expressions may not parse reliably.

Being aware of these assumptions helps you understand when you can trust the results and when additional care is needed.

Practical Uses and Accessibility

This converter is useful in several everyday and professional contexts:

• Check and document writing: Verify that the written amount on a check or contract matches the digits.
• Invoices and receipts: Spell out totals in words to reduce the risk of tampering or misreading.
• Education: Help students practice reading and writing numbers, reinforcing place value concepts.
• Accessibility: Pair numeric data with words so that screen readers can announce values clearly.
• Data entry and validation: Cross-check handwritten or spoken numbers by converting them to a consistent form.

Because all calculations happen locally in your browser, the tool works offline after it loads and does not transmit your inputs to a server. This makes it suitable for sensitive or private numbers where you prefer not to use a networked service.

Summary

The Number ↔ Words Converter gives you a reliable way to move between digits and English number words within a well-defined range. By following standard cardinal wording, clear hyphenation rules, and a short-scale interpretation of large numbers, it balances accuracy with ease of use. As long as you stay within the documented limits—non-negative integers up to 999,999,999 and standard English phrasing—you can rely on the outputs for documents, learning, and accessibility tasks.