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SI Prefix Converter

Scale quantities across all 24 SI prefixes, from quetta to quecto, plus unprefixed units. Distinguish case-sensitive symbols and retain exact powers of ten.

Your content stays on your device Free, with no account
Clear units. Explicit assumptions. Local conversion · no uploads
Decimal/scientific notation. Up to 120 digits; exponent −500 to 500. Use a dot, without commas or unit names.
Choose one unpowered unit. Mass prefixes attach to gram (g); compound or squared units are not parsed.
Display rounding only. Exact values remain available where the definitions are exact.

Includes all 24 SI prefixes plus no prefix. Prefixes are case-sensitive: m is milli; M is mega. Prefixes act on one unpowered unit symbol; mass prefixes attach to gram, not kilogram. Binary data prefixes are separate.

YOUR CONVERSION

Enter values to convert.

Unit conventions: BIPM SI prefixes ↗. Exact definitions are derived algebraically; π-based angular values are explicitly approximate.

A FEW SIMPLE STEPS

How to use SI Prefix Converter

  1. Enter your value and select the source and target units. Results update locally as inputs change.
  2. Set any required quantity basis or reference. Includes all 24 SI prefixes plus no prefix. Prefixes are case-sensitive: m is milli; M is mega. Prefixes act on one unpowered unit symbol; mass prefixes attach to gram, not kilogram. Binary data prefixes are separate.
  3. Choose significant digits with the slider or exact input. Review the result, factors and quantity details.
  4. Copy the result or download a TXT report. Clear releases the entered value and result; category shortcuts open other standalone converters.
PRIVATE BY DESIGN

Why use this tool?

Your values and assumptions remain on your device. Self-hosted JavaScript uses exact fraction arithmetic for defined factors before display rounding; angular values involving π disclose their approximation. No account, upload, remote API or saved input history is used.

Tool inputs stay in your browser. Only your theme preference is saved on this device.

A few things worth knowing

What does this converter support?

Scale quantities across all 24 SI prefixes, from quetta to quecto, plus unprefixed units. Distinguish case-sensitive symbols and retain exact powers of ten.

Which definitions and assumptions apply?

Includes all 24 SI prefixes plus no prefix. Prefixes are case-sensitive: m is milli; M is mega. Prefixes act on one unpowered unit symbol; mass prefixes attach to gram, not kilogram. Binary data prefixes are separate.

Are the results exact?

Defined rational/decimal conversion factors are applied with exact integer fractions before rounding to 2–12 significant digits. Approximate displayed values are marked ≈. Radian conversions use a disclosed 50-decimal approximation of π. Exact math cannot improve the precision of your original measurement or correct unsuitable reference conditions.

What input formats are supported?

Use a decimal dot and optional scientific notation, with up to 120 digits, 180 characters and exponents from −500 to 500. Angle Converter also accepts signed DDD:MM:SS when DMS is selected. The tool reports invalid quantities, zero reciprocals or missing references rather than keeping an old result.

Are values uploaded or stored?

No. All conversion runs locally in the page. Results are copied or downloaded only when you choose. The website stores only the theme preference. Switching standalone pages does not transfer your inputs.

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