GlenCalc

Specific heat calculator

Heating water takes about 4.18 kJ per kilogram per degree Celsius. Add a heater’s power to see how long it would take with no heat lost.

Water 4,184. Other materials: look up their specific heat capacity.

Your answer

Heat energy needed334,720 joules
In kilowatt-hours0.093 kWh
In kilocalories80 kcal
Time at that power (no losses)2 min 47 s
  • Melting or boiling takes extra energy (latent heat) that this doesn’t include: about 2,257 kJ per kg to turn water to steam.

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How we worked it out

Updated as you change the numbers.

  1. Q = m × c × ΔT.
  2. Time = energy ÷ power (watts are joules per second).

Method and assumptions

Specific heat capacity is the energy to warm 1 kg by 1 °C (1 K). Real heaters lose some heat to the surroundings, so actual times are longer.

Questions

How much energy does it take to heat 1 kg of water from 20 °C to 100 °C?

334.7 kJ (0.093 kWh). A 2,000 W kettle would take about 2 minutes 47 seconds with no losses.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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