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).
What is kilocalorie (dietary)?
A kilocalorie, written as Calorie with a capital C in nutrition contexts, is a unit of energy equal to 1,000 thermochemical calories. It is the standard unit used to express the energy content of food on nutrition labels globally.
Real-world uses
Kilocalories are the standard unit for food energy labelling in the United States (labelled as "Calories" with a capital C), dietary planning, and exercise energy expenditure. A typical adult needs about 2,000 kcal/day. Fitness trackers report calories burned in kcal.
History
Wilbur Atwater pioneered the use of kilocalories for food energy measurement in the 1890s. The confusing convention of using a capital-C "Calorie" to mean kilocalorie originated in American nutritional science and persists on US food labels today.
Common mistakes
The most common mistake is confusing Calories (kcal) with calories (cal)—they differ by a factor of 1,000. When food labels say "100 Calories," they mean 100 kilocalories. Also, assuming all macronutrients have the same caloric density (fat has 9 kcal/g vs 4 kcal/g for protein and carbohydrates).
When is this conversion used?
Converting between therm (US) and kilocalorie (dietary) 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. Nutritional information is labelled in kilocalories in some countries and kilojoules in others, making this conversion important for dietary planning and food science.
Worked examples
1 therm (US) = 25,216.53919694 kilocalorie (dietary)
1 kilocalorie (dietary) = 4,184 joule
How to convert therm (US) to kilocalorie (dietary)
To convert therm (US) to kilocalorie (dietary), multiply the value by 25,216.53919694.
To convert kilocalorie (dietary) back to therm (US), multiply by 0.00003966.
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: therm (US) to kilocalorie (dietary)
| therm (US) | kilocalorie (dietary) |
|---|---|
| 0.1 | 2,521.65391969 |
| 0.5 | 12,608.26959847 |
| 1 | 25,216.53919694 |
| 2 | 50,433.07839388 |
| 5 | 126,082.6959847 |
| 10 | 252,165.39196941 |
| 25 | 630,413.47992352 |
| 50 | 1,260,826.95984704 |
| 100 | 2,521,653.91969407 |
| 250 | 6,304,134.79923518 |
| 500 | 12,608,269.59847036 |
| 1,000 | 25,216,539.19694073 |
Common values
| therm (US) | kilocalorie (dietary) | |
|---|---|---|
| A food calorie (1 kcal) | 0.00003966 therm (US) | 1 kilocalorie (dietary) |
| A AA battery | 0.00008872 therm (US) | 2.23709369 kilocalorie (dietary) |
| Boiling a kettle | 0.00398082 therm (US) | 100.38240918 kilocalorie (dietary) |
| Daily human diet (2000 kcal) | 0.07931302 therm (US) | 2,000 kilocalorie (dietary) |
| 1 gallon of gasoline | 1.24883893 therm (US) | 31,491.3957935 kilocalorie (dietary) |
Available Energy units
More therm (US) conversions
- Convert therm (US) to joule
- Convert therm (US) to kilojoule
- Convert therm (US) to kilowatt hour
- Convert therm (US) to calorie (thermochemical)
- Convert therm (US) to kilocalorie (dietary)
- Convert therm (US) to watt hour
- Convert therm (US) to megajoule
- Convert therm (US) to electronvolt
- Convert therm (US) to British thermal unit
Assumption: calorie means thermochemical calorie, and therm means US therm.