What is megajoule?

A megajoule is a unit of energy equal to one million joules. It is used in industrial energy calculations, explosive yield estimations, and large-scale thermodynamic systems.

Real-world uses

Megajoules are used in energy analysis for fuel content (1 litre of petrol contains about 34.2 MJ), building energy ratings, and industrial process energy requirements. Life cycle assessment (LCA) studies report embodied energy in MJ per unit of material.

History

The megajoule became a standard unit in energy engineering and policy analysis during the 20th century. It provides a convenient scale for comparing fuel energy content, industrial processes, and building energy performance across different energy sources.

Common mistakes

Confusing MJ with MWh—1 MWh = 3,600 MJ. Also, when comparing fuel energy densities, failing to distinguish between lower heating value (LHV) and higher heating value (HHV), which can differ by 5–10% for hydrocarbon fuels.

What is therm (US)?

A US therm is a unit of energy equal to 100,000 BTU. It is used by gas utility companies in the United States as the standard billing unit for natural gas consumption.

Real-world uses

The therm is used in the United States and United Kingdom for natural gas billing. One therm equals 100,000 BTU (approximately 29.3 kWh). Residential gas bills in the US often list consumption in therms. It is also used in industrial gas metering and procurement contracts.

History

The therm was introduced as a practical unit for natural gas billing in the early 20th century, when gas supply companies needed a convenient large-scale energy unit for residential and commercial customers. It consolidated prior inconsistent measurement practices in the gas industry.

Common mistakes

Confusing the therm with the BTU—1 therm = 100,000 BTU. Also, the US therm and the UK therm differ slightly (the UK therm is based on 105.5 MJ, while the US therm is exactly 100,000 BTU ≈ 105.48 MJ). Not to be confused with the thermie (a metric unit of heat).

When is this conversion used?

Converting between megajoule and therm (US) is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.

Worked examples

1 megajoule = 0.00947813 therm (US)

1 therm (US) = 105,506,000 joule

How to convert megajoule to therm (US)

To convert megajoule to therm (US), multiply the value by 0.00947813.

To convert therm (US) back to megajoule, multiply by 105.506.

Measurement standards

The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.

Did you know?

A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.

Quick reference: megajoule to therm (US)

megajoule	therm (US)
0.1	0.00094781
0.5	0.00473907
1	0.00947813
2	0.01895627
5	0.04739067
10	0.09478134
25	0.23695335
50	0.4739067
100	0.94781339
250	2.36953349
500	4.73906697
1,000	9.47813394

Common values

	megajoule	therm (US)
A food calorie (1 kcal)	0.004184 megajoule	0.00003966 therm (US)
A AA battery	0.00936 megajoule	0.00008872 therm (US)
Boiling a kettle	0.42 megajoule	0.00398082 therm (US)
Daily human diet (2000 kcal)	8.368 megajoule	0.07931302 therm (US)
1 gallon of gasoline	131.76 megajoule	1.24883893 therm (US)

Available Energy units

More megajoule conversions

Assumption: calorie means thermochemical calorie, and therm means US therm.