Heat converters
Specific Heat Capacity Converter
Convert J/(kg·K), kJ/(kg·°C), cal/(g·°C) and BTU/(lb·°F).
Result
1 BTU/(lb·°F)
4186.8 J/(kg·K) = 1 BTU/(lb·°F)
All units for this value
| Unit | Symbol | Value |
|---|---|---|
| Joule per kilogram per kelvin | J/(kg·K) | 4186.8 |
| Joule per kilogram per °C | J/(kg·°C) | 4186.8 |
| Kilojoule per kilogram per kelvin | kJ/(kg·K) | 4.1868 |
| Joule per gram per °C | J/(g·°C) | 4.1868 |
| Calorie (IT) per gram per °C | cal/(g·°C) | 1 |
| Kilocalorie (IT) per kilogram per °C | kcal/(kg·°C) | 1 |
| BTU (IT) per pound per °F | BTU/(lb·°F) | 1 |
| BTU (IT) per pound per °R | BTU/(lb·°R) | 1 |
| Foot-pound force per pound per °R | ft·lbf/(lb·°R) | 778.169 |
About this calculator
Specific heat capacity measures how much energy it takes to raise the temperature of one unit of mass by one degree, a property that differs enormously between materials like water, metal, and air. This converter switches between metric units such as J/(kg·K), calorie-based units, and the BTU/(lb·°F) unit common in US engineering references.
How it works in plain English
Specific heat capacity combines an energy unit, a mass unit, and a temperature-interval unit into one compound measurement. The converter treats joule per kilogram per kelvin as its common anchor, so any entered value is first rescaled into that base unit and then rescaled again into whichever target unit you choose. Because a kelvin and a Celsius degree represent the same size of temperature step, J/(kg·K) and J/(kg·°C) are numerically identical, even though they look different.
The calorie-based units here use the International Table calorie, defined as exactly 4.1868 joules, which is the standard used in most modern engineering and food-energy tables rather than the slightly different thermochemical calorie. The BTU-based units use the International Table BTU, equal to exactly 1055.05585262 joules, combined with the pound (0.45359237 kg) and a Fahrenheit degree, which is five-ninths the size of a kelvin. That five-ninths factor is why BTU/(lb·°F) numbers look so different from their metric equivalents even for the same physical substance.
Pick a from and to unit, enter a value, and the result updates immediately, with a full table showing the same specific heat capacity across every supported unit at once. A precision control adjusts how many decimal places are displayed, and a swap button reverses the two selected units in a single click.
The formula
- value_in_target = value_in_source × (source factor to J/(kg·K)) ÷ (target factor to J/(kg·K))
- 1 cal(IT)/(g·°C) = 1 kcal(IT)/(kg·°C) = 4186.8 J/(kg·K)
- 1 BTU(IT)/(lb·°F) = 1055.05585262 ÷ (0.45359237 × 5/9) = 4186.8 J/(kg·K)
- 1 kJ/(kg·K) = 1000 J/(kg·K)
Worked example
Water has a specific heat capacity of about 4186.8 J/(kg·K), and suppose you want that figure expressed in BTU/(lb·°F) to compare against a US engineering table. Dividing 4186.8 by the BTU/(lb·°F) factor of 4186.8 gives exactly 1, since the BTU/(lb·°F) unit was itself defined so that water's specific heat comes out to almost exactly 1 in that unit.
Entering 4186.8 into the J/(kg·K) field with BTU/(lb·°F) selected as the target returns 1.0 immediately. The full unit table also shows this same value equals 1 kcal/(kg·°C), 4.1868 J/(g·°C), and 4.1868 kJ/(kg·K), all calculated from that single entered figure at once.
Specific heat capacity of common substances
| Substance | Specific heat capacity (J/(kg·K)) |
|---|---|
| Water (liquid, 15 °C) | 4186.8 |
| Ice | 2100 |
| Aluminium | 897 |
| Iron / steel | 449 |
| Copper | 385 |
| Air (sea level) | 1005 |
| Glass | 840 |
Standard engineering reference values
Frequently asked questions
Why is water's specific heat capacity almost exactly 1 in some units?
Both the calorie and the BTU were historically defined around the amount of energy needed to warm water by one degree, so kcal/(kg·°C) and BTU/(lb·°F) naturally come out close to 1 for water. This converter uses the modern International Table definitions of those units, which is why the value lands at almost exactly 1.0 rather than a rounder or messier number.
What's the difference between J/(kg·K) and J/(kg·°C)?
Nothing in practice: a one-kelvin temperature step and a one-degree-Celsius temperature step are exactly the same size, only the zero points of the two scales differ. Since specific heat capacity describes a change per degree rather than a specific temperature, the two units are numerically identical and interchangeable.
Which calorie and BTU does this converter use?
It uses the International Table (IT) calorie, defined as exactly 4.1868 joules, and the International Table BTU, defined as exactly 1055.05585262 joules. These are the versions most commonly used in modern engineering, HVAC, and food-energy references, as opposed to older thermochemical definitions that differ by a small fraction of a percent.
Why does a material with a high specific heat capacity heat up slowly?
A higher specific heat capacity means more energy is needed to raise each unit of mass by one degree, so for the same energy input, a material with a high value warms up less than one with a low value. Water's relatively high capacity is one reason large bodies of water moderate nearby air temperatures.
Can I compare specific heat capacities of very different materials directly?
Yes, once everything is expressed in the same unit. Type each material's known value into the from field in its original unit, convert to a common unit like J/(kg·K), and read off the results from the table. This avoids manually tracking calorie, BTU, and metric conversion factors for each comparison.
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