# 周波数変換

> Convert rpm to Hz, Hz to rpm, BPM to Hz, GHz to MHz and hertz to radians per second (ω = 2πf), from Hz to THz.

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

One hertz is one cycle per second, so revolutions per minute and beats per minute divide by 60 to give hertz, and the SI prefixes step by 1,000 from kHz to THz. Angular frequency in radians per second is ω = 2πf, so 1 Hz is 6.2832 rad/s; conversions to or from rad/s involve π and are shown to 12 significant figures.

The default converts 3,000 rpm to 50 Hz, the speed of a two-pole motor on a 50 Hz supply. Musicians convert tempo the same way (120 BPM is 2 Hz), and radio users move between MHz and GHz: 2.4 GHz Wi-Fi is 2,400 MHz.

Rpm and BPM count whole cycles per minute, while rad/s counts the angle swept per second. A cycle is 2π radians, so 60 rpm is 1 Hz and 6.2832 rad/s.

## 入力

- **値**: 変換元の単位で数値を入力するか、単位付きの数値を入力します
- **変換元** (選択肢：hertz (Hz), kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz), revolution per minute (rpm), beat per minute (BPM), radian per second (rad/s))
- **変換先** (選択肢：hertz (Hz), kilohertz (kHz), megahertz (MHz), gigahertz (GHz), terahertz (THz), revolution per minute (rpm), beat per minute (BPM), radian per second (rad/s))

## 結果

- 変換後の値 — 主な結果
- 単位換算
- 換算係数
- 正確さ

## 計算式

$$
\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{Hz} \end{gathered}
$$

## 計算例

### 3000 rpm in Hz

- 値: 3000 rpm
- 変換元: revolution per minute (rpm)
- 変換先: hertz (Hz)
- **変換後の値: 50 Hz**
- 照合元：3000 / 60 = 50

### 120 BPM in Hz

- 値: 120 BPM
- 変換元: beat per minute (BPM)
- 変換先: hertz (Hz)
- **変換後の値: 2 Hz**
- 照合元：120 / 60 = 2

### 1 Hz in rad/s

- 値: 1 Hz
- 変換元: hertz (Hz)
- 変換先: radian per second (rad/s)
- **変換後の値: 6.2831853072 rad/s**
- **正確さ: 定義は正確、πを含む**
- 照合元：ω = 2πf = 6.28318530717958647… (Python decimal)

### 2.4 GHz in MHz

- 値: 2.4 GHz
- 変換元: gigahertz (GHz)
- 変換先: megahertz (MHz)
- **変換後の値: 2,400 MHz**
- 照合元：2.4 × 1000

## よくある質問

### How do I convert rpm to Hz?

Divide by 60, because hertz counts cycles per second and rpm cycles per minute. 3,000 rpm is 50 Hz, 1,800 rpm is 30 Hz, and 7,200 rpm, a common hard-drive speed, is 120 Hz. To go from Hz to rpm, multiply by 60.

### Why does a motor run at 3,000 or 3,600 rpm?

Because its speed is locked to the supply frequency. A synchronous motor turns at 120 × f ÷ p rpm, where p is the number of poles, so a two-pole motor runs at 3,000 rpm on 50 Hz mains and 3,600 rpm on 60 Hz. Induction motors run a few percent below this synchronous speed, for example 2,900 rpm on 50 Hz.

### How do I convert Hz to rad/s?

Multiply by 2π, about 6.28319: ω = 2πf. 50 Hz is 314.16 rad/s and 1 Hz is 6.2832 rad/s. Both units reduce to “per second”, but a hertz counts whole cycles while a radian per second counts the angle swept, and one cycle is 2π radians.

### How many Hz is 120 BPM?

2 Hz: 120 beats ÷ 60 seconds. Tempo in beats per minute converts to hertz by dividing by 60, so 90 BPM is 1.5 Hz. The same rule applies to heart rate: the American Heart Association's normal adult resting range of 60 to 100 beats per minute is 1 to 1.67 Hz.

### How many MHz are in a GHz?

1,000. SI prefixes step by 1,000: 1 GHz = 1,000 MHz = 1,000,000 kHz = 10⁹ Hz. Wi-Fi's 2.4 GHz band is 2,400 MHz, and a 3.5 GHz processor clock ticks 3.5 billion times a second. Frequency prefixes are always decimal, never the binary 1,024 used for some memory sizes.

### 「周波数変換」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：4。 例えば、「3000 rpm in Hz」は3000 / 60 = 50と照合しています。

### この計算方法の出典は何ですか？

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement.

## 出典

- [NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C — General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)