数値フォーマッター
任意の数値をロケール区切り、科学的記数法、工学的記数法、英語の言葉、略語、ローマ数字などに一度にフォーマットします。
このツールについて
任意の数値（非常に大きい値または小さい値を含む）を入力すると、あらゆる有用なフォーマットで即座に表示されます：ロケール区切り（1,234,567.89）、科学的記数法（1.23 × 10⁶）、工学的記数法（1.23 × 10⁶）、英数字（one million two hundred…）、略式表記（1.23M）、ローマ数字（3999以下の整数）、バイナリ、16進数、8進数、パーセンテージ。別の通貨フォーマッターで記号プレフィックスを設定し、小数点以下の桁数を選択できます。各フォーマットされた結果には独自のコピーボタンがあります。
使い方
- 1 入力フィールドに任意の数値を入力または貼り付けてください。フォーマットが即座に更新されます。
- 2 フォーマットされた結果パネルをスクロールしてすべての表現を一度に確認してください。
- 3 通貨セクションを使用して通貨フォーマットの記号と小数精度を設定してください。
- 4 任意のフォーマットの隣にあるコピーアイコンをクリックして、その特定の表現をクリップボードにコピーしてください。
One number, every useful representation
A single number can be written in many forms depending on who is reading it. An accountant wants thousands separators; a scientist wants powers of ten; a marketer wants "1.2M"; a programmer wants hexadecimal. This tool takes one input number and renders it simultaneously as locale-formatted text, scientific notation, engineering notation, an abbreviated shorthand, English words, a percentage, a Roman numeral, and binary, hexadecimal, and octal. A separate currency formatter lets you add a symbol and fix the decimal places. Each result has its own copy button.
How each format is computed
| Format | Rule | Example for 1234567.89 |
|---|---|---|
| Locale | Group digits in threes with separators | 1,234,567.89 |
| Scientific | Mantissa between 1 and 10 times a power of ten | 1.234568 × 10^6 |
| Engineering | Like scientific, but the exponent is a multiple of 3 | 1.234568 × 10^6 |
| Abbreviated | K/M/B/T/Q suffix for thousands, millions, … | 1.235M |
| Percentage | Multiply by 100 and add % | 123,456,789% |
| Roman | Integer part, 1–3999 only | N/A (out of range) |
| Binary / Hex / Octal | Rounded integer in base 2 / 16 / 8 | (of the rounded integer) |
The difference between scientific and engineering notation is worth understanding. Scientific notation always puts one non-zero digit before the decimal point, so the exponent can be any integer. Engineering notation restricts the exponent to multiples of three so the result lines up with metric prefixes — 10^3 is kilo, 10^6 is mega, 10^9 is giga. Engineers prefer it because the power of ten maps directly onto units they actually use.
A worked example with the number 2024
Enter 2024 and the tool shows: locale 2,024; scientific 2.024000 × 10^3; engineering 2.024 × 10^3; abbreviated 2.024K; words two thousand twenty-four; percentage 202,400%; Roman numeral MMXXIV; binary 11111101000; hexadecimal 0x7E8; octal 0o3750. The Roman numeral is built by greedily subtracting the largest values — 2024 = 1000 + 1000 + 10 + 10 + (5−1) → M M X X IV — which is exactly how Roman numerals are constructed.
Limits and rounding you should know about
- Roman numerals stop at 3,999. Standard Roman numerals have no symbol above M used in this way, so the tool returns
N/Afor 0, negatives, fractions, and anything 4,000 or larger. - Binary, hex, and octal use the integer part only. These bases convert the number rounded to the nearest whole number, so
10.9is treated as11. They are also computed on a 32-bit unsigned value, which is the right model for typical programming use but not for arbitrarily huge integers. - Words handle decimals as digit-by-digit.
3.14becomes "three point one four", reading each fractional digit separately — the standard way to speak a decimal. - Floating-point precision. Very large or very precise values inherit the limits of the browser's double-precision arithmetic; the tool rounds the mantissa to a sensible number of digits rather than showing meaningless trailing noise.
The currency formatter
The currency panel is separate because it has its own choices. You pick a symbol (default $) and a number of decimal places (default 2). The tool then formats your number with grouped thousands and a fixed decimal count and prepends the symbol — for example 1234.5 with symbol € and 2 decimals becomes €1,234.50. Set decimals to 0 for whole-currency display, or higher for currencies and crypto that use more decimal places.
Use cases
- Writing out cheque or contract amounts where the figure must also appear in words.
- Reading engineering or lab values in proper scientific or engineering notation.
- Programming, where you need the same value in decimal, hex, binary, and octal at once.
- Design and dashboards, grabbing an abbreviated
1.2Mlabel for a compact display.
Everything is calculated in your browser the instant you type, so no number you enter is sent anywhere, and you get all ten formats at once without switching tools.