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Science & Engineering

Heat Energy Calculator

Calculate the heat energy to warm or cool a material with Q = mcΔT, in kJ, kWh, kcal and BTU.

Your inputs

Results

Heat energy to add

668.96 kJ

In kWh
0.18582 kWh
In kilocalories
159.885 kcal
In BTU
634.05 BTU

≈Estimate based on the stated model and assumptions

Notes for this result

  • Sensible heat only: assumes no phase change (melting or boiling) between the two temperatures and a constant specific heat.

What this calculator does

Sensible heat is the energy that changes temperature without a phase change.

Formula and method

Q = m × c × (T₂ − T₁)
m
mass (kg)
c
specific heat (J/(kg·K))
ΔT
temperature change (K or °C)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Substance: Water (liquid, ~25 °C) — 4181 J/(kg·K)
  • Mass: 2 kg
  • Start temperature: 20 °C
  • End temperature: 100 °C

Results

  • Heat energy to add: 668.96 kJ
  • In kWh: 0.18582 kWh
  • In kilocalories: 159.885 kcal
  • In BTU: 634.05 BTU

How to read the results

Water’s high specific heat makes it slow to heat and good at storing energy.

Assumptions and limitations

  • Phase changes (melting, boiling) need latent heat and are not included.
  • Specific heats are typical values near room temperature.

These are educational estimates. Electrical, structural and other safety-critical work must comply with local codes and be designed or checked by a qualified professional.

Questions

How much energy to boil a kettle?

Heating 1 L of water from 20 to 100 °C needs about 335 kJ, roughly 0.093 kWh, before losses.

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

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