Printf Numbers

printf is the workhorse format that shaped how the world prints numbers - the format string %010.2f is a small language of its own, telling a printer the width, the padding, the sign and the precision in a single line. From log files to invoices, that grammar still decides exactly how every value looks.

Printf Numbers brings the same grammar to your browser: choose the base (2, 8, 10 or 16), the field width, the padding character, whether to force a sign, and how many decimals to keep, and the tool renders the value - showing you the equivalent format spec as you go. Every rule follows printf faithfully, and the result copies or downloads in one click.

• True printf rules: Width, padding, sign, left alignment and precision all behave like the C formatter.
• Four bases: Print in binary, octal, decimal or hexadecimal with uppercase letters.
• Zero or space padding: Choose the filler that fills the field up to the width.
• Forced sign: Show an explicit plus for positive values, or keep only real negatives.
• Exact precision: Decimals round to the number of places you ask for.
• Live spec preview: The printf string is written for you as you adjust the options.
• Copy or download: The formatted result exports in one click.
• Free and private: Everything runs locally; nothing is uploaded or stored.

1. Enter a value - integer or decimal, positive or negative.
2. Pick a base - binary, octal, decimal or hexadecimal.
3. Set the width, padding and precision - and optionally force a plus sign.
4. Watch the spec - the printf format is written for you as you go.
5. Copy or download the formatted number for logs, reports or code.

Example 1 - The classic pad. Enter 3.5, width 10, zero padding, precision 2: 0000003.50 - the %010.2f look.

Example 2 - Plain width. Enter 42, width 6, space padding: " 42" - five spaces then 42.

Example 3 - Left aligned. Enter 42, width 6, left aligned: "42 " - the number leads and spaces trail.

Example 4 - Forced sign. Enter 42 with plus forced, width 5, zeros: +0042 - the sign leads the padding.

Example 5 - Hexadecimal. Enter 255, base 16, width 4, zeros: 00FF - the byte that is 0xFF printed in a tidy field.

• Faithful printf: The output matches what C programmers expect - no surprises when you port it.
• Fixed-width tables: Pad values to a width for aligned columns in logs and reports.
• Exact big values: Formatting works from the digits, so large numbers are not rounded by a float.
• Four bases ready: Switch binary, octal, decimal or hex without learning new syntax.
• Live spec feedback: The equivalent format string is shown, so you learn printf while you use it.
• Private and free: All formatting stays in the browser; nothing is uploaded or logged.