速度換算ツール

正確な係数で mph から km/h、km/h から mph、m/s、ノットへ換算します。ft/s、海面高度のマッハ数、光速にも対応します。

更新日 2026年9月29日検証済みの例：5

変換後の値

km/h

有効桁数：12；最も近い値へ、等距離ならゼロから遠い値へ

単位換算: 60 mph = 96.56064 km/h
換算係数: 1.609344
正確さ: 正確

60 mphは正確に96.56064 km/hです。 1単位のマイル毎時は正確に1.609344 km/hです。

同じ量を各単位で表示

60 mphを各速さ単位で表示行数：8

単位	値	定義
メートル毎秒 (m/s)	26.8224	基本単位
キロメートル毎時 (km/h)	96.56064	1 km/h = 1,000/3,600 m/s、正確な値
マイル毎時 (mph)	60	1 mph = 0.44704 m/s、正確な値
ノット (kn)	52.13857	1 kn = 1,852/3,600 m/s、正確な値
foot per second (ft/s)	88	1 ft/s = 0.3048 m/s、正確な値
kilometre per second (km/s)	0.0268224	1 km/s = 1,000 m/s、正確な値
Mach (sea level) (Ma)	0.07882125	1 Ma = 340.294 m/s、近似値（海面上のISA空気中の音速、15 °C）
speed of light (c)	8.94699 × 10⁻⁸	1 c = 299,792,458 m/s、正確な値

計算方法 S

マイル毎時からメートル毎秒へ換算
$60\ \text{mph} \times 0.44704\ \tfrac{\text{m/s}}{\text{mph}} = 26.8224\ \text{m/s}$
1 mph = 0.44704 m/s、正確な値
メートル毎秒からキロメートル毎時へ換算
$26.8224\ \text{m/s} \div \tfrac{1{,}000}{3{,}600}\ \tfrac{\text{m/s}}{\text{km/h}} = 96.56064\ \text{km/h}$
1 km/h = 1,000/3,600 m/s、正確な値
統合した換算係数
$1\ \text{mph} = \frac{0.44704}{\tfrac{1{,}000}{3{,}600}}\ \text{km/h} = 1.609344\ \text{km/h}$
両方の単位の定義が正確で、変換後の値は有限小数なので、表示されるすべての桁が正確です。

速度換算ツールについて

Each speed unit is a fixed number of metres per second. The road and sea units are exact: a mile per hour is 0.44704 m/s because the mile is 1,609.344 m, a kilometre per hour is 1/3.6 m/s, and a knot, one nautical mile per hour, is 1,852/3,600 m/s.

The default converts 60 mph to 96.56064 km/h, the figure a UK or US driver needs on metric roads. Sailors and pilots work in knots, and 1 knot is exactly 1.852 km/h.

Mach is fixed here at 340.294 m/s, the speed of sound in the International Standard Atmosphere at sea level and 15 °C, and results that use it are marked approximate because the real speed of sound falls with temperature. The speed of light is exactly 299,792,458 m/s by definition.

計算例

60 mph in km/h

値: 60 mph
変換元: mile per hour (mph)
変換先: kilometre per hour (km/h)

変換後の値: 96.56064 km/h
正確さ: 正確

照合元：60 × 1609.344 m / 1000 = 96.56064 km/h (1 mi = 1609.344 m, NIST HB 44)

1 knot in km/h

値: 1 kn
変換元: knot (kn)
変換先: kilometre per hour (km/h)

変換後の値: 1.852 km/h

照合元：1 knot = 1 nautical mile per hour = 1852 m/h (NIST SP 811 App. B)

100 km/h in m/s

値: 100 km/h
変換元: kilometre per hour (km/h)
変換先: metre per second (m/s)

変換後の値: 27.7777777778 m/s
正確さ: 定義は正確、結果は循環小数

照合元：100000 m / 3600 s = 250/9 (Python 3.8 fractions from the legal definitions)

Speed of light in km/s

値: 1 c
変換元: speed of light (c)
変換先: kilometre per second (km/s)

変換後の値: 299,792.458 km/s

照合元：c = 299,792,458 m/s exactly (SI definition of the metre)

よくある質問

How do I convert mph to km/h?

Multiply by 1.609344: 60 mph × 1.609344 = 96.56064 km/h, and 70 mph is 112.65 km/h. The factor is exact because a mile is exactly 1,609.344 m. Multiplying by 1.6 is a mental shortcut that comes out 0.6% low; to go from km/h to mph, multiply by 0.621371.

How do I convert km/h to m/s?

Divide by 3.6, because an hour has 3,600 seconds and a kilometre 1,000 metres. 100 km/h is 27.78 m/s and 36 km/h is exactly 10 m/s. Multiply by 3.6 to go back: a sprinter at 10 m/s is running 36 km/h, or 22.37 mph.

What is a knot in mph and km/h?

One knot is exactly 1.852 km/h, about 1.15078 mph or 0.514444 m/s. It is one nautical mile (1,852 m) per hour, the speed unit of shipping and aviation, so a 30-knot wind is 55.56 km/h or 34.52 mph.

How fast is Mach 1?

In the International Standard Atmosphere at sea level (15 °C) it is 340.294 m/s, which is 1,225.06 km/h or 761.22 mph, the value this converter uses. The speed of sound depends on air temperature, so at 11 km altitude, where the standard atmosphere is −56.5 °C, Mach 1 is about 295 m/s or 1,062 km/h.

Why is the speed of light an exact number?

Because the metre is defined from it. Since 1983 the metre has been the distance light travels in vacuum in 1/299,792,458 of a second, which fixes c at exactly 299,792,458 m/s, or 1,079,252,848.8 km/h. Converting c into any unit here is therefore exact.

「速度換算ツール」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、「60 mph in km/h」は60 × 1609.344 m / 1000 = 96.56064 km/h (1 mi = 1609.344 m, NIST HB 44)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.

この計算機について

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

出典

出典と照合済み

この計算機には、独立した出典の解答を使った計算例が 5 件あります。テストに組み込まれており、ここでも実行できます。

同じ量を各単位で表示

マイル毎時からメートル毎秒へ換算

メートル毎秒からキロメートル毎時へ換算

統合した換算係数