SI Prefixes Studio
From the width of a DNA helix to the mass of the galaxy. Master the powers of ten with our interactive explorer and converter.
The Language of Magnitude
Science deals with extremes that the human mind struggles to comprehend. We study neutrinos that pass through the Earth and galaxies light-years away. Writing these numbers out (0.000... or 1,000...) is not only impractical but prone to error. The SI (Système International) prefixes act as a universal shorthand, compressing these vast zeros into simple, standardized syllables like "Nano" or "Giga".
Mastering these prefixes is more than just memorizing a table; it's about developing an intuition for the scale of reality. When a biologist hears "micrometer," they think of cells. When a physicist hears "femtosecond," they think of lasers. This studio helps you build that intuition.
Mapping the Universe
Understanding these prefixes gives you a map of the universe, from the subatomic to the cosmic:
The Macroscopic World (> 1m)
- Terra (T, 10¹²)1 TrillionThe scale of modern data. A 1TB hard drive holds 1 trillion bytes.
- Peta (P, 10¹⁵)1 QuadrillionDistance light travels in one year is about 9.4 Petameters.
- Exa (E, 10¹⁸)1 QuintillionThe age of the Universe is approximately 0.43 Exaseconds.
The Microscopic World (< 1m)
- Micro (μ, 10⁻⁶)1 MillionthSize of biological machinery. Red blood cells are ~8 micrometers wide.
- Nano (n, 10⁻⁹)1 BillionthThe atomic scale. Silicon transistors are now just 3-5 nanometers.
- Femto (f, 10⁻¹⁵)1 QuadrillionthFemtosecond lasers can capture chemical reactions in real-time.
A History of Standards
The journey to these prefixes began during the French Revolution in 1795, giving us "kilo", "hecto", "deca", "deci", "centi", and "milli". It took over 160 years for the system to be formalized as the "International System of Units" (SI) in 1960. Since then, science has pushed the boundaries further out (galaxies) and further in (quarks), necessitating expansion.
The 2022 Update
In late 2022, scientists officially adopted Ronna/Quetta and Ronto/Quecto. Why? Because global data storage is rapidly approaching the "Yottabyte" limit, and we needed names for what comes next.
Memorization Hack
Need to remember the order for a physics exam? Try these mnemonics:
- Large Scale: Kill My Giant Turtle Please Eat Zebra Yogurt.
(Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta) - Small Scale: millipedes make nice pets for all zebra youths.
(milli, micro, nano, pico, femto, atto, zepto, yocto)
Frequently Asked Questions
What are the newest SI prefixes?
In 2022, the 27th General Conference on Weights and Measures (CGPM) officially added four new prefixes: Ronna (R) for 10^27, Quetta (Q) for 10^30, Ronto (r) for 10^-27, and Quecto (q) for 10^-30. These were introduced to handle the growing data needs (ronnaybytes) and subatomic measurements.
Why is 'Kilo' lowercase 'k' but 'Mega' uppercase 'M'?
It's a historical inconsistency that became standardized. Generally, prefixes with a magnitude of 10^6 (Mega) and above are capitalized to distinguish them from base units. Prefixes from 10^3 (kilo) down to 10^-30 (quecto) are lowercase. 'Kilo' (k) was established in 1795, long before the 'capital for large' rule was adopted in 1960.
How do I convert Micro to Milli?
Think of the order of magnitude. Milli (10^-3) is larger than Micro (10^-6). Specifically, their difference in exponents is (-3) - (-6) = +3. This means 1 Milli = 10^3 (or 1000) Micro. Conversely, to convert Micro to Milli, you divide by 1000.
What comes after Tera?
The order of ascending magnitude after Tera (T, 10^12) is: Peta (P, 10^15), Exa (E, 10^18), Zetta (Z, 10^21), Yotta (Y, 10^24), Ronna (R, 10^27), and Quetta (Q, 10^30).
What is the smallest thing we can currently measure?
We routinely measure at the 'Femto' scale (10^-15) for atomic nuclei radii. 'Atto' (10^-18) is used in attosecond physics to track electron motion. While 'Quecto' (10^-30) exists as a prefix, we haven't experimentally measured anything that small yet—the Planck length is around 10^-35 meters!
Why does the metric system use powers of 10?
The metric system, born from the French Revolution, was designed to be universal and rational. Using a base-10 (decimal) system matches our ten fingers and makes calculations trivial just by shifting the decimal point, unlike the imperial system which uses arbitrary factors like 12 (feet) or 16 (ounces).
Is 'Angstrom' an SI prefix?
No. The Angstrom (Å) is a specific unit of length commonly used in crystallography and spectroscopy, equal to 10^-10 meters (or 0.1 nanometers). It is notably NOT an official SI prefix, although it is still widely accepted for use with SI units.
Who decides on new prefixes?
The International Bureau of Weights and Measures (BIPM) helps coordinate these decisions, which are ratified by the General Conference on Weights and Measures (CGPM). It takes decades for new prefixes to be approved—before 2022, the last update was in 1991 (Zetta/Yotta).
What is the 'Google' number prefix?
There isn't an SI prefix for a 'Googol' (10^100). The largest official prefix is 'Quetta' (10^30). A Google is a mathematical curiosity, not a practical unit for physical measurement, as it exceeds the number of particles in the observable universe.
How do binary prefixes (KiB, MiB) differ from metric ones (KB, MB)?
Great question! Metric prefixes are strictly decimal (1 KB = 1000 bytes). Computing often uses binary (2^10 = 1024). To resolve confusion, 'Binary Prefixes' were created: Kibi (Ki = 1024), Mebi (Mi = 1024^2), Gibi (Gi = 1024^3). However, in common marketing, 'GB' is still often used to mean 10^9 or 2^30 interchangeably, causing confusion.