エネルギー単位換算

ジュール、カロリー、英熱量、電子ボルトの正確な定義を使い、kWh から BTU、カロリーからジュール、kcal から kJ、サームから kWh に換算します。

更新日 2026年9月29日検証済みの例：4

変換後の値

BTU

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: 1 kWh ≈ 3,412.142 BTU
換算係数: 3,412.14163313
正確さ: 定義は正確、結果は循環小数

1 kWhは約3,412.142 BTUです。

同じ量を各単位で表示

1 kWhを各エネルギー単位で表示行数：14

単位	値	定義
joule (J)	3,600,000	基本単位
キロジュール (kJ)	3,600	1 kJ = 1,000 J、正確な値
megajoule (MJ)	3.6	1 MJ = 1,000,000 J、正確な値
watt-hour (Wh)	1,000	1 Wh = 3,600 J、正確な値
kilowatt-hour (kWh)	1	1 kWh = 3,600,000 J、正確な値
megawatt-hour (MWh)	0.001	1 MWh = 3,600,000,000 J、正確な値
calorie (cal)	860,420.7	1 cal = 4.184 J、正確な値（熱化学カロリー）
キロカロリー (kcal)	860.4207	1 kcal = 4,184 J、正確な値
British thermal unit (BTU)	3,412.142	1 BTU = 1,055.05585262 J、正確な値
therm (US) (thm)	0.03412956	1 thm = 105,480,400 J、正確な値
electronvolt (eV)	2.246943 × 10²⁵	1 eV = 1.602176634 × 10⁻¹⁹ J、正確な値
erg	36,000,000,000,000	1 erg = 1 × 10⁻⁷ J、正確な値
foot-pound (ft·lbf)	2,655,224	1 ft·lbf = 1.3558179483314004 J、正確な値
tonne of oil equivalent (toe)	0.00008598452	1 toe = 41,868,000,000 J、正確な値

計算方法 S

kilowatt-hourからjouleへ換算
$1\ \text{kWh} \times 3{,}600{,}000\ \tfrac{\text{J}}{\text{kWh}} = 3{,}600{,}000\ \text{J}$
1 kWh = 3,600,000 J、正確な値
jouleからBritish thermal unitへ換算
$3{,}600{,}000\ \text{J} \div 1{,}055.05585262\ \tfrac{\text{J}}{\text{BTU}} = 3{,}412.14163313\ \text{BTU}$
1 BTU = 1,055.05585262 J、正確な値
統合した換算係数
$1\ \text{kWh} = \frac{3{,}600{,}000}{1{,}055.05585262}\ \text{BTU} \approx 3{,}412.14163313\ \text{BTU}$
両方の単位の定義は正確ですが、変換後の値は循環小数です。有効数字12桁で表示します。

エネルギー単位換算について

Every energy unit is a fixed number of joules. A kilowatt-hour is exactly 3.6 MJ (1,000 W for 3,600 s), the thermochemical calorie is 4.184 J, and the International Table British thermal unit is 1,055.05585262 J (NIST SP 811), so each factor is a definition rather than a measurement.

The default converts 1 kWh to 3,412.14 BTU, the link between electricity bills and heating or air-conditioning ratings. Food energy is the other everyday use: a food Calorie is a kilocalorie, so a 2,000 kcal day is 8,368 kJ.

Some units share a name but not a size. The International Table calorie (4.1868 J) is 0.07% larger than the thermochemical one used here, and the US therm (105,480,400 J) is defined with the 59 °F BTU, so it comes to 99,976 International Table BTU rather than 100,000.

計算例

1 kWh in BTU

値: 1 kWh
変換元: kilowatt-hour (kWh)
変換先: British thermal unit (BTU)

変換後の値: 3,412.14163313 BTU

照合元：3,600,000 J ÷ 1055.05585262 J (International Table BTU, NIST SP 811 App. B) (Python 3.8 fractions from the legal definitions)

1 kcal in kJ

値: 1 kcal
変換元: kilocalorie (kcal)
変換先: kilojoule (kJ)

変換後の値: 4.184 kJ
正確さ: 正確

照合元：Thermochemical calorie = 4.184 J exactly (NIST SP 811 App. B)

1 eV in joules

値: 1 eV
変換元: electronvolt (eV)
変換先: joule (J)

変換後の値: 1.602176634 × 10⁻¹⁹ J

照合元：e = 1.602176634 × 10⁻¹⁹ C exactly (SI 2019), so 1 eV = 1.602176634 × 10⁻¹⁹ J

1 US therm in BTU

値: 1 thm
変換元: therm (US) (thm)
変換先: British thermal unit (BTU)

変換後の値: 99,976.1289775 BTU

照合元：105,480,400 J (NIST SP 811 App. B) ÷ 1055.05585262 J (Python 3.8 fractions from the legal definitions)

よくある質問

How many BTU are in a kWh?

3,412.14 BTU. A kWh is 3,600,000 J and the International Table BTU is 1,055.05585262 J, so 3,600,000 ÷ 1,055.05585262 = 3,412.1416. In the other direction 1 BTU is 0.000293071 kWh, so 100,000 BTU of heat is 29.31 kWh.

How many joules are in a calorie?

4.184 J for the thermochemical calorie used here, or 4.1868 J for the International Table calorie; NIST SP 811 lists both. Nutrition labels count kilocalories, often printed as “Calories”, so one food Calorie is 4,184 J or 4.184 kJ. EU food labels give energy in both kJ and kcal.

What is a unit of electricity?

One kilowatt-hour, 3.6 MJ: the energy a 1,000 W appliance uses in one hour. Electricity bills in the UK and India count “units” in kWh, so a 2 kW heater running for 3 hours uses 6 units, and a 10 W LED bulb takes 100 hours to use one.

What is the difference between kW and kWh?

A kilowatt measures power, the rate at which energy is used; a kilowatt-hour measures the energy itself, power multiplied by time. A 3 kW kettle running for 4 minutes uses 3 × 4/60 = 0.2 kWh. Convert kW with the power converter and kWh with this one.

How many kWh are in a therm?

29.3 kWh. The US therm is 105,480,400 J (NIST SP 811), which is 29.3001 kWh; the EU and UK therm, 100,000 International Table BTU or 105,505,585.262 J, is 29.3071 kWh. The two differ by 0.024%, so either rounds to 29.3 kWh.

「エネルギー単位換算」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、「1 kWh in BTU」は3,600,000 J ÷ 1055.05585262 J (International Table BTU, NIST SP 811 App. B) (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.

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{J} \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 4 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

kilowatt-hourからjouleへ換算

jouleからBritish thermal unitへ換算

統合した換算係数