🔢

Metric Prefixes & Scientific Notation

Q: What is the difference between MB and MiB?

MB (megabyte) usually means decimal 1,000,000 bytes; MiB (mebibyte) means binary 1,048,576 bytes. Hard drive manufacturers use decimal, operating systems often report binary — the difference matters for large drives.

Q: How do I write a number in scientific notation?

Move the decimal point so exactly one non-zero digit is left of it; the number of places moved is the exponent. 0.0045 → 4.5 × 10⁻³ (moved right 3 places).

Q: Is 1 cm exactly 1 inch divided by 2.54?

By international definition, 1 inch = exactly 2.54 cm, so 1 cm = 1/2.54 in = 0.3937007874 in.

The SI metric prefixes defined by NIST SP 330, plus the binary prefixes used in computing. Use this sheet to move decimal points correctly and convert between decimal and scientific notation.

Kilo

×10³

1 km = 10³ m = 1,000 m

Example: 5 km = 5,000 m = 3.11 miles

Centi

×10⁻²

1 cm = 10⁻² m = 0.01 m

Example: 2.54 cm = 1 inch (exact, by definition)

Milli

×10⁻³

1 mm = 10⁻³ m = 0.001 m

Example: 25.4 mm = 1 inch (exact)

Micro

×10⁻⁶

1 µm = 10⁻⁶ m

Example: Human hair ≈ 17–180 µm wide

Nano

×10⁻⁹

1 nm = 10⁻⁹ m

Example: DNA helix ≈ 2 nm wide

Mega (binary)

×2²⁰

1 MiB = 2²⁰ bytes = 1,048,576 B

Example: Operating systems commonly report 1 "MB" = 1,048,576 bytes (binary)

Giga (binary)

×2³⁰

1 GiB = 2³⁰ bytes = 1,073,741,824 B

Example: 8 GiB RAM = 8 × 1,073,741,824 bytes

Scientific notation

standard form

a × 10ⁿ where 1 ≤ a < 10

Example: 0.0045 = 4.5 × 10⁻³; 6,700,000 = 6.7 × 10⁶

Practice the conversion too

These examples convert US customary to metric using the exact NIST / SI constants. Open a converter to check any value:

Browse all converters →

Frequently Asked Questions

What is the difference between MB and MiB?

MB (megabyte) usually means decimal 1,000,000 bytes; MiB (mebibyte) means binary 1,048,576 bytes. Hard drive manufacturers use decimal, operating systems often report binary — the difference matters for large drives.

How do I write a number in scientific notation?

Move the decimal point so exactly one non-zero digit is left of it; the number of places moved is the exponent. 0.0045 → 4.5 × 10⁻³ (moved right 3 places).

Is 1 cm exactly 1 inch divided by 2.54?

By international definition, 1 inch = exactly 2.54 cm, so 1 cm = 1/2.54 in = 0.3937007874 in.

More formula sheets

📐 Geometry 🌡️ Temperature ⚡ Physics 🔁 Conversion Formulas

Last Updated 2026 | Formulas are standard textbook content; conversion constants trace to NIST SP 330 & the BIPM SI Brochure.