🔢 SI Decimal Prefixes Converter 2026
Convert between all SI metric prefixes — from yocto (10⁻²⁴) to yotta (10²⁴)
1 kilo = 1,000 base
Multiply by 10³
1 kilo × 10³ = 1,000 base units
📊 Value in All Prefixes
Complete SI Prefix Table
| Symbol | Prefix | Exponent | Factor | Decimal |
|---|---|---|---|---|
| Y | yotta | 10²⁴ | 10²⁴ | 1,000,000,000,000,000,000,000,000 |
| Z | zetta | 10²¹ | 10²¹ | 1,000,000,000,000,000,000,000 |
| E | exa | 10¹⁸ | 10¹⁸ | 1,000,000,000,000,000,000 |
| P | peta | 10¹⁵ | 10¹⁵ | 1,000,000,000,000,000 |
| T | tera | 10¹² | 10¹² | 1,000,000,000,000 |
| G | giga | 10⁹ | 10⁹ | 1,000,000,000 |
| M | mega | 10⁶ | 10⁶ | 1,000,000 |
| k | kilo | 10³ | 10³ | 1,000 |
| h | hecto | 10² | 10² | 100 |
| da | deka | 10¹ | 10¹ | 10 |
| — | BASE | 10⁰ | 10⁰ | 1 |
| d | deci | 10⁻¹ | 10⁻¹ | 0.1 |
| c | centi | 10⁻² | 10⁻² | 0.01 |
| m | milli | 10⁻³ | 10⁻³ | 0.001 |
| µ | micro | 10⁻⁶ | 10⁻⁶ | 0.000001 |
| n | nano | 10⁻⁹ | 10⁻⁹ | 0.000000001 |
| p | pico | 10⁻¹² | 10⁻¹² | 0.000000000001 |
| f | femto | 10⁻¹⁵ | 10⁻¹⁵ | 0.000000000000001 |
| a | atto | 10⁻¹⁸ | 10⁻¹⁸ | 0.000000000000000001 |
| z | zepto | 10⁻²¹ | 10⁻²¹ | 0.000000000000000000001 |
| y | yocto | 10⁻²⁴ | 10⁻²⁴ | 0.000000000000000000000001 |
Understanding SI Prefixes
🔢 Decimal System
Powers of 10. Each prefix differs by factor of 10, 100, or 1000. Moving between adjacent "common" prefixes (k, M, G, T) = ×1000.
📊 Common Prefixes
Everyday: kilo (k, 10³), mega (M, 10⁶), giga (G, 10⁹). Small: milli (m, 10⁻³), micro (µ, 10⁻⁶), nano (n, 10⁻⁹).
💻 Data Storage
Binary vs decimal: In computing, "kilo" often means 1024 (2¹⁰). SI kilo = 1000. IEC uses KiB, MiB, GiB for binary.
📐 Usage Rule
Combine prefix + unit: 5 km = 5 kilometers. Don't stack prefixes (no "milli-kilo"). One prefix per unit only.
Frequently Asked Questions
What are SI prefixes?
Metric prefixes denoting powers of 10. Adopted by the
International System of Units (SI). Range from 10⁻²⁴ (yocto) to 10²⁴ (yotta). Applied to any SI unit.
How do I convert between prefixes?
Multiply or divide by powers of 10. Moving to smaller prefix:
multiply. Moving to larger: divide. Example: 1 km = 1000 m (multiply by 10³).
What does kilo mean?
Kilo (k) = 10³ = 1,000. Greek "chilioi" = thousand. 1 kg = 1000 g.
1 km = 1000 m. Most common prefix for everyday use.
What does mega mean?
Mega (M) = 10⁶ = 1,000,000. Greek "megas" = great. 1 MW =
1,000,000 W. 1 MB = 1,000,000 bytes (in SI).
What does giga mean?
Giga (G) = 10⁹ = 1 billion. Greek "gigas" = giant. 1 GHz =
1,000,000,000 Hz. Common for computer speeds and storage.
What does tera mean?
Tera (T) = 10¹² = 1 trillion. Greek "teras" = monster. 1 TB =
1,000,000,000,000 bytes. Used for large data storage.
What does milli mean?
Milli (m) = 10⁻³ = 0.001. Latin "mille" = thousand (1/1000). 1 mm
= 0.001 m. 1 mg = 0.001 g.
What does micro mean?
Micro (µ) = 10⁻⁶ = 0.000001. Greek "mikros" = small. Symbol is
Greek letter mu. 1 µm = 0.000001 m (micrometer).
What does nano mean?
Nano (n) = 10⁻⁹ = 0.000000001. Greek "nanos" = dwarf. 1 nm =
0.000000001 m. Used for atoms, molecules, semiconductors.
How many bytes in a gigabyte?
SI: 10⁹ = 1,000,000,000 bytes. Binary (GiB): 2³⁰ = 1,073,741,824
bytes. Windows uses binary, most others use SI. Difference ≈ 7%.
What is the difference between SI and binary prefixes?
SI: powers of 10 (k=1000, M=10⁶). Binary (IEC):
powers of 2 (Ki=1024, Mi=2²⁰). Binary uses "i" suffix: KiB, MiB, GiB.
What is the largest SI prefix?
Yotta (Y) = 10²⁴. Added in 1991. Rarely used in practice. Data
centers might reach yottabytes eventually.
What is the smallest SI prefix?
Yocto (y) = 10⁻²⁴. Added in 1991. Used for extremely small
quantities like particle physics measurements.
Can I combine prefixes?
No! Never use double prefixes like "millikilogram". Use base unit
with appropriate prefix. 1000 kg = 1 megagram (Mg) or 1 tonne.
Why is kilogram the base unit, not gram?
Historical accident. The original standard (1799) was a kilogram
mass. SI kept it as base unit. Prefixes apply to gram: mg, µg (not mkg).
What prefixes are used most commonly?
Common large: kilo (1000), mega (10⁶), giga (10⁹), tera (10¹²).
Common small: milli (10⁻³), micro (10⁻⁶), nano (10⁻⁹).
How accurate is this prefix converter?
Uses exact powers of 10. Mathematically precise. Results shown in
both standard notation and scientific notation where appropriate.