# 流量変換

> 米ガロンと立方フィートの正確な値で、ポンプ・配管・換気のL/minからgpm、gpmからL/min、cfmからm³/h、m³/hからL/sへの換算を行います。

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

Flow rate is volume per time, and each unit here is a fixed number of cubic metres per second. The US gallon (3.785411784 L) and the cubic foot (28.316846592 L) are exact, so litres per minute, gallons per minute and cubic feet per minute convert with no rounding in the factors.

The default converts 10 L/min to 2.64 US gpm, close to the 2.5 gpm (9.46 L/min) of a standard US showerhead. Plumbers and pump buyers use L/min and gpm, fan and compressor ratings use cfm or m³/h, and river flows are reported in m³/s (cumecs).

The gallon here is the US gallon. An imperial gallon per minute is 4.54609 L/min, 20% more, so check which gallon a specification uses before converting it.

## 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：cubic metre per second (m³/s), cubic metre per hour (m³/h), litre per second (L/s), litre per minute (L/min), litre per hour (L/h), US gallon per minute (gal/min), cubic foot per minute (ft³/min))
- **変換先** (選択肢：cubic metre per second (m³/s), cubic metre per hour (m³/h), litre per second (L/s), litre per minute (L/min), litre per hour (L/h), US gallon per minute (gal/min), cubic foot per minute (ft³/min))

## 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

$$
\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{m³/s} \end{gathered}
$$

## 計算例

### 10 L/min in US gal/min

- 値: 10 L/min
- 変換元: litre per minute (L/min)
- 変換先: US gallon per minute (gal/min)
- **変換後の値: 2.6417205236 gal/min**
- 照合元：10 L ÷ 3.785411784 L = 1250000000/473176473 (Python 3.8 fractions from the legal definitions)

### 1 m³/s in L/s

- 値: 1 m³/s
- 変換元: cubic metre per second (m³/s)
- 変換先: litre per second (L/s)
- **変換後の値: 1,000 L/s**
- 照合元：1 m³ = 1000 L

### 1 cfm in L/min

- 値: 1 ft³/min
- 変換元: cubic foot per minute (ft³/min)
- 変換先: litre per minute (L/min)
- **変換後の値: 28.316846592 L/min**
- 照合元：1 ft³ = 0.3048³ m³ = 28.316846592 L (NIST HB 44 App. C)

### 1 m³/h in L/s

- 値: 1 m³/h
- 変換元: cubic metre per hour (m³/h)
- 変換先: litre per second (L/s)
- **変換後の値: 0.2777777778 L/s**
- **正確さ: 定義は正確、結果は循環小数**
- 照合元：1000 L / 3600 s = 5/18

## よくある質問

### How do I convert L/min to gpm?

Divide by 3.785411784, or multiply by 0.264172. 10 L/min is 2.64 US gpm and 20 L/min is 5.28 gpm. To go from US gpm to L/min, multiply by 3.785, so a 2.5 gpm showerhead runs at 9.46 L/min.

### How do I convert cfm to m³/h?

Multiply by 1.69901. A cubic foot is 0.028316846592 m³ and an hour is 60 minutes, so 1 cfm = 1.69901079552 m³/h exactly. A 100 cfm bathroom fan moves 169.9 m³/h, or 47.2 L/s. To go from m³/h to cfm, multiply by 0.588578.

### What is a normal shower flow rate?

The US EPA puts standard showerheads at 2.5 gallons per minute, 9.46 L/min, and requires WaterSense-labelled ones to use no more than 2.0 gpm, 7.57 L/min. A 10-minute shower at 2.5 gpm uses 25 gallons, or 94.6 litres. Timing how long your shower takes to fill a 1-litre jug gives your own figure: 6 seconds means 10 L/min.

### How do I convert m³/h to L/s?

Divide by 3.6. A cubic metre is 1,000 litres and an hour 3,600 seconds, so 1 m³/h = 1,000/3,600 = 0.2778 L/s, a repeating decimal. A pump rated at 36 m³/h delivers exactly 10 L/s, or 600 L/min.

### Is gpm in US or imperial gallons?

In this converter, US gallons: 1 gpm = 3.785411784 L/min. Imperial gallons per minute are 4.54609 L/min, 20% larger, and appear on equipment specified in imperial units. To convert an imperial figure, multiply it by 1.20095 to get US gpm before entering it.

### 「流量変換」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、「10 L/min in US gal/min」は10 L ÷ 3.785411784 L = 1250000000/473176473 (Python 3.8 fractions from the legal definitions)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)