# SI and metric prefix converter

> Convert between SI metric prefixes such as giga, mega, kilo, milli, micro and nano, from quecto (10⁻³⁰) to quetta (10³⁰), including the 2022 additions.

操作できるページ：https://www.calcopenly.com/ja/conversion/si-prefix-converter
分野：単位換算ツール

An SI prefix multiplies a unit by a power of ten: kilo is 10³, mega 10⁶, milli 10⁻³ and nano 10⁻⁹. Converting between two prefixes multiplies the value by 10 raised to the difference of their exponents, which moves the decimal point without changing any digits. The converter covers all 24 SI prefixes, from quecto (10⁻³⁰) to quetta (10³⁰).

Engineers and students use it to move between scales of one unit. The default turns the 2.4 GHz Wi-Fi band into 2,400 MHz, a shift of three powers of ten. The unit symbol field only labels the result, so the same conversion works for metres, grams, hertz or watts.

Two BIPM rules apply to every prefix: prefixes are never combined (write nm, not mµm), and because the kilogram already carries one, prefixes attach to the gram: 1 mg, not 1 µkg.

## 入力

- **値**
- **変換元** (選択肢：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), none (10⁰), 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))
- **変換先** (選択肢：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), none (10⁰), 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))
- **Unit symbol**: Only used for labels, e.g. m, g, Hz, W

## 結果

- 変換後の値 — 主な結果
- 単位換算
- Shift in powers of ten

## 計算式

$$
x_{\text{to}} = x_{\text{from}} \times 10^{\,e_{\text{from}} - e_{\text{to}}}
$$

## 計算例

### 2.4 GHz in MHz

- 値: 2.4
- 変換元: giga (G, 10⁹)
- 変換先: mega (M, 10⁶)
- Unit symbol: Hz
- **変換後の値: 2,400 MHz**
- **単位換算: 2.4 GHz = 2,400 MHz**
- **Shift in powers of ten: 3**
- 照合元：giga = 10⁹, mega = 10⁶ (SI Brochure Table 7): 2.4 × 10³

### 1 km in m

- 値: 1
- 変換元: kilo (k, 10³)
- 変換先: none (10⁰)
- Unit symbol: m
- **変換後の値: 1,000 m**
- 照合元：kilo = 10³

### 1 quetta in yotta (2022 prefix)

- 値: 1
- 変換元: quetta (Q, 10³⁰)
- 変換先: yotta (Y, 10²⁴)
- Unit symbol: g
- **変換後の値: 1,000,000 Yg**
- **Shift in powers of ten: 6**
- 照合元：quetta = 10³⁰ (CGPM 2022), yotta = 10²⁴

### Smallest to largest: quecto to quetta

- 値: 1
- 変換元: quecto (q, 10⁻³⁰)
- 変換先: quetta (Q, 10³⁰)
- Unit symbol: g
- **Shift in powers of ten: -60**
- **変換後の値: 1 × 10⁻⁶⁰ Qg**
- 照合元：10⁻³⁰ / 10³⁰ = 10⁻⁶⁰

### 5 µs in ns

- 値: 5
- 変換元: micro (µ, 10⁻⁶)
- 変換先: nano (n, 10⁻⁹)
- Unit symbol: s
- **変換後の値: 5,000 ns**
- 照合元：micro = 10⁻⁶, nano = 10⁻⁹: 5 × 10³

## よくある質問

### What are the SI prefixes in order?

There are 24. From largest: quetta (Q, 10³⁰), ronna (R, 10²⁷), yotta (Y, 10²⁴), zetta (Z), exa (E), peta (P), tera (T), giga (G), mega (M), kilo (k, 10³), hecto (h, 10²) and deca (da, 10¹). Then the submultiples: deci (d), centi (c), milli (m, 10⁻³), micro (µ), nano (n), pico (p), femto (f), atto (a), zepto (z), yocto (y), ronto (r) and quecto (q, 10⁻³⁰).

### What are the newest SI prefixes?

Ronna (R, 10²⁷), quetta (Q, 10³⁰), ronto (r, 10⁻²⁷) and quecto (q, 10⁻³⁰), adopted by the 27th General Conference on Weights and Measures (CGPM) in November 2022. They were the first additions since zetta, yotta, zepto and yocto in 1991. On the new scale the Earth's mass, about 5.97 × 10²⁴ kg, is roughly 6 ronnagrams.

### How do I convert between metric prefixes?

Subtract the exponents and move the decimal point that many places. From giga (10⁹) to mega (10⁶) is 9 − 6 = 3 places to the right, so 2.4 GHz = 2,400 MHz; from micro (10⁻⁶) to nano (10⁻⁹) is also 3 places, so 5 µs = 5,000 ns. Moving to a larger prefix shifts the point left: 1,500 m = 1.5 km.

### Why is kilo a lowercase k but mega an uppercase M?

The SI writes the symbols for multiples from mega (M, 10⁶) upward in capitals, while kilo (k), hecto (h), deca (da) and every submultiple are lowercase. The case changes the value: 1 MW (megawatt) is 10⁹ times 1 mW (milliwatt). Writing K for kilo is wrong in the SI, because K is the symbol for the kelvin.

### Does kilo mean 1,000 or 1,024 in computing?

In the SI, kilo always means exactly 1,000, so 1 kbit = 1,000 bits and 1 GB = 10⁹ bytes (NIST). For powers of two the IEC approved binary prefixes in December 1998: 1 KiB (kibibyte) = 1,024 bytes and 1 GiB = 2³⁰ = 1,073,741,824 bytes. The gap grows with size, which is why a 1 TB drive shows about 931 GiB.

### 「SI and metric prefix converter」の精度はどのくらいですか？

精度は入力値と計算方法の前提に依存します。十進演算には有効数字50桁を使いますが、推定、数値計算手法、元データの精度はそれより低い場合があります。表示の丸め処理でこれらの制約がなくなるわけではありません。 独立した出典の解答と照合した計算例：5。 例えば、「2.4 GHz in MHz」はgiga = 10⁹, mega = 10⁶ (SI Brochure Table 7): 2.4 × 10³と照合しています。

### この計算方法の出典は何ですか？

BIPM — The International System of Units (SI Brochure, 9th ed.), Table 7: SI prefixes; BIPM — CGPM 2022 Resolution 3: ronna, quetta, ronto, quecto.

## 出典

- [BIPM — The International System of Units (SI Brochure, 9th ed.), Table 7: SI prefixes](https://www.bipm.org/en/publications/si-brochure)
- [BIPM — CGPM 2022 Resolution 3: ronna, quetta, ronto, quecto](https://www.bipm.org/en/cgpm-2022/resolution-3)