Specific Heat Capacity Calculator
The heat needed to change a material’s temperature — and how long a given heater takes to deliver it.
Q = mcΔT: heat equals mass times specific heat capacity times temperature change.
How the specific heat capacity calculator works
Q = mcΔT: heat equals mass times specific heat capacity times temperature change. Water's capacity of 4,186 J/(kg·K) is unusually high, which is why the sea moderates climate and why a kettle takes as long as it does.
The time is the practical part: two litres of water from 20 to 100 °C needs 670 kJ, and a 2.4 kW kettle takes about five minutes to deliver it — assuming no losses, which is why the real kettle takes longer.
Formula: Q = mcΔT; t = Q / power
Worked examples
| Inputs | Heat required (J) | Note |
|---|---|---|
| Two litres of water to boiling | 669,760 | 670 kJ, about five minutes |
| Cooling instead | -125,580 | negative heat — energy released |
| Aluminium | 143,520 | a quarter of the energy |
FAQFrequently asked questions
What is specific heat capacity?
The energy needed to raise one kilogram of a material by one kelvin. Water is 4,186 J/(kg·K), which is unusually high.
Why does water take so long to heat?
Because of that high capacity. It takes about four and a half times as much energy per kilogram as aluminium and ten times as much as copper.
Does this include boiling?
No. Turning water to steam needs a further 2.26 MJ per kilogram of latent heat, which dwarfs the heating.
Why is my kettle slower than the calculation?
Losses to the air, the kettle body and the element. Ninety per cent efficiency is typical, and the last few degrees are the slowest.
Is a kelvin the same as a degree Celsius?
For a difference, yes — exactly. Only the zero point differs, which is why ΔT is the same in both.
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 Measurement Institute — Australia's measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.