Heat Capacity Calculator
The heat needed to change a material's temperature — with the time it takes at a given power, and the cost of the energy.
How much energy to heat something up.
How the heat capacity calculator works
Q = mcΔT: mass × specific heat capacity × temperature change. Specific heat is how much energy one kilogram needs per degree, and it varies enormously — water is 4,186 J/kg·K, roughly ten times steel.
That is why water is the standard coolant and why coastal climates are mild: it takes an enormous amount of energy to move the sea's temperature at all.
Formula: Q = m c ΔT
Worked examples
| Inputs | Energy required | Note |
|---|---|---|
| 2 kg of water by 60 K | 502,320 J | 502 kJ — about 4 minutes at 2 kW |
| The same mass of steel | 55,920 J | a ninth of the energy |
| A kettle of water | 569,296 J | 569 kJ |
FAQFrequently asked questions
What is specific heat capacity?
The energy needed to raize one kilogram of a substance by one degree. Water's 4,186 J/kg·K is unusually high.
Why does water take so much energy?
Hydrogen bonding. Much of the added energy goes into breaking bonds rather than raizing the temperature, which is why water moderates climate so effectively.
How long does a kettle take?
About 285 seconds for 1.7 L from 20°C to 100°C on a 2 kW element, before losses. Real kettles run a little longer.
Does this include melting or boiling?
No. Phase changes absorb energy at constant temperature — that is latent heat, and it is a separate and much larger term.
Why do metals feel colder than wood at the same temperature?
Conductivity, not heat capacity. Metal draws heat from your hand far faster, even though it holds less per kilogram.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G, g₀, R, c
- NIST Special Publication 811 — Guide for the use of the International System of Units — unit conversions
- The Engineering ToolBox — material properties — specific heats, expansion coefficients, densities
- National Institute of Standards and Technology — the US measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.