Metric Prefix Converter (µF to nF, kΩ, MHz)

About the Metric Prefix Converter (µF to nF, kΩ, MHz)

Change the prefix of a value without changing its size: 4.7 µF = 4,700 nF = 4,700,000 pF, 2.2 kΩ = 2,200 Ω, 2.4 GHz = 2,400 MHz. Type the value with its prefix and unit — 4.7 µF, 4.7uF, 100 nanofarads, or an RKM code such as 4k7 — and choose the prefix you want. You also get the value in every prefix from quecto (10⁻³⁰) to quetta (10³⁰), in scientific and engineering notation, and with the neatest prefix for it.

The arithmetic is exact, so there are no rounding errors such as 4,699.999999. Units with a power are handled correctly (1 km² is 1,000,000 m², not 1,000), and a binary mode adds kibi, mebi, gibi and the other IEC prefixes for bits and bytes: 1 GB = 0.931322574615478515625 GiB.

Common uses

• Reading capacitor and resistor values across datasheets, schematics and parts lists that use different prefixes.
• Checking homework and lab results in physics, chemistry and electronics.
• Writing values in engineering notation for reports and specifications.
• Working out what KiB, MiB and GiB mean next to kB, MB and GB.

The SI prefixes

• quetta Q 10³⁰ · ronna R 10²⁷ · yotta Y 10²⁴ · zetta Z 10²¹ · exa E 10¹⁸ · peta P 10¹⁵
• tera T 10¹² · giga G 10⁹ · mega M 10⁶ · kilo k 10³ · hecto h 10² · deca da 10¹
• deci d 10⁻¹ · centi c 10⁻² · milli m 10⁻³ · micro µ 10⁻⁶ · nano n 10⁻⁹ · pico p 10⁻¹²
• femto f 10⁻¹⁵ · atto a 10⁻¹⁸ · zepto z 10⁻²¹ · yocto y 10⁻²⁴ · ronto r 10⁻²⁷ · quecto q 10⁻³⁰

Ronna, quetta, ronto and quecto are the newest, added by Resolution 3 of the 27th General Conference on Weights and Measures. The list is Table 7 of the BIPM SI Brochure (see also BIPM: SI prefixes).

How to convert between prefixes

Each prefix is a power of ten, so moving to a smaller prefix multiplies the number and moving to a larger one divides it: value in the new prefix = value × 10^(old exponent − new exponent). From µ (10⁻⁶) to n (10⁻⁹) is three powers of ten down, so 4.7 µF × 1,000 = 4,700 nF.

With a unit raised to a power, the prefix is raised too, because a prefix and its unit form one new unit: 1 km² = (1,000 m)² = 1,000,000 m², and 2.3 cm³ = 2.3 × 10⁻⁶ m³ — the SI Brochure’s own example.

Rules for writing prefixes

• The prefix is written straight onto the unit, without a space: kΩ, MHz, µF.
• Case matters: m is milli and M mega, so 1 mHz is a thousandth of a hertz and 1 MHz a million hertz. Kilo is a lower-case k; capital K is the kelvin.
• Only one prefix at a time: write nF, not mµF.
• Mass prefixes go on the gram: 1 mg, not 1 µkg — the kilogram is the only SI unit with a prefix in its name.
• µ is the micro sign; where it cannot be typed, u is often used (uF), and the converter reads it as µ.

Scientific and engineering notation

Scientific notation writes a number as m × 10ⁿ with 1 ≤ m < 10: 0.000047 = 4.7 × 10⁻⁵. Engineering notation keeps the exponent a multiple of 3 — 47 × 10⁻⁶ — so it lines up with the prefixes: 10⁻⁶ is micro, and 47 × 10⁻⁶ F is 47 µF, with the number between 1 and 999.

Binary prefixes: KiB, MiB, GiB

SI prefixes are always powers of 10: a kilobyte is 1,000 bytes. For powers of 2, IEC 80000-13 defines kibi (Ki) 2¹⁰ = 1,024, mebi (Mi) 2²⁰, gibi (Gi) 2³⁰, tebi (Ti) 2⁴⁰ and so on up to robi (Ri) 2⁹⁰ and quebi (Qi) 2¹⁰⁰. A 1 TB drive therefore holds about 931 GiB (0.909 TiB). Turn on Binary prefixes to convert between the two, or use the data storage converter for bytes and bits.

RKM codes on resistors and capacitors

Parts lists and small components often print values without a decimal point: the prefix letter takes its place, as set out in IEC 60062. 4K7 is 4.7 kΩ, R47 0.47 Ω, 4R7 4.7 Ω, 2M2 2.2 MΩ and 4L7 4.7 mΩ; for capacitors, 4n7 is 4.7 nF, 2p2 2.2 pF and 4u7 4.7 µF. Type the code and the converter reads it as ohms (R, K, M, G, T, L) or farads (p, n, u, m, F).

Limitations

• The unit is a label: the converter changes the prefix, not the unit itself (it does not turn farads into coulombs or metres into feet). For other units, use the unit converter.
• One prefix per value: compound prefixes such as mµF are refused, as the SI requires.
• Results with more than about 20 digits are shown in scientific notation.
• Binary prefixes are meant for bits and bytes; with other units the result has no standard meaning.

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