Thermal Energy Calculator
Solve sensible heat Q = m·c·ΔT in all four directions, latent heat Q = m·L, power–time energy Q = P·t, and convert energy units. Everything runs in your browser.
Which tool for which question?
• This tool = total thermal ENERGY in joules: heating a mass, melting/boiling, energy from any power source over time.
• joule-heating = electric heating specifically: power from current through resistance (P = I²R).
• wattage-calculator = appliance wattage, power-supply sizing, electricity bills.
• Heat transfer RATE (how fast heat flows, W) is a different question this tool does not answer.
• This tool = total thermal ENERGY in joules: heating a mass, melting/boiling, energy from any power source over time.
• joule-heating = electric heating specifically: power from current through resistance (P = I²R).
• wattage-calculator = appliance wattage, power-supply sizing, electricity bills.
• Heat transfer RATE (how fast heat flows, W) is a different question this tool does not answer.
Sensible heat solver — Q = m·c·ΔT
Choose what to solve for, then fill in the other three values. Delta-T in K or °C is identical (it is a difference).
Latent heat solver — Q = m·L
Phase change at constant temperature: melting, boiling, condensing. Choose what to solve for.
Power & time — Q = P·t
Energy delivered by any power source over time. Choose what to solve for.
Energy unit converter
Formula reference
| Solve for | Given | Formula |
|---|---|---|
| Energy Q (sensible) | m, c, ΔT | Q = m·c·ΔT |
| Mass m | Q, c, ΔT | m = Q / (c·ΔT) |
| Specific heat c | Q, m, ΔT | c = Q / (m·ΔT) |
| ΔT | Q, m, c | ΔT = Q / (m·c) |
| Energy Q (latent) | m, L | Q = m·L |
| Mass m (latent) | Q, L | m = Q / L |
| Latent heat L | Q, m | L = Q / m |
| Energy Q (power) | P, t | Q = P·t |
| Power P | Q, t | P = Q / t |
| Time t | Q, P | t = Q / P |
Frequently asked questions
What is thermal energy?
Thermal energy is the total internal energy of the particles in a substance, the sum of their kinetic and potential energies. In practice you usually want the energy you must ADD or REMOVE: sensible heat for a temperature change (Q = m times c times delta-T), latent heat for a phase change at constant temperature (Q = m times L), or the energy delivered by a heater over time (Q = P times t). This calculator solves all three.
How do I calculate sensible heat?
Use Q = m times c times delta-T, where m is mass in kg, c is specific heat in J/kg K, and delta-T is the temperature change in K (same as degrees C for a difference). Example: 2 kg of water (c = 4186 J/kg K) heated from 20 C to 80 C (delta-T = 60 K) needs Q = 2 times 4186 times 60 = 502320 J, which is 502.32 kJ, about 120.057 kcal, or 0.139533 kWh.
How do I solve for delta-T, mass, or specific heat?
Fill in any three of the four quantities and the calculator solves the fourth. For delta-T: 41860 J absorbed by 0.5 kg of water gives delta-T = 41860 / (0.5 times 4186) = 20 K. For mass: 19250 J into copper (c = 385) with delta-T = 100 K gives m = 19250 / (385 times 100) = 0.5 kg. For specific heat: 41860 J, 1 kg, delta-T = 10 K gives c = 41860 / (1 times 10) = 4186 J/kg K.
What is latent heat and how is it calculated?
Latent heat is the energy of a phase change at constant temperature, Q = m times L. Melting 1 kg of ice (L = 334000 J/kg) takes Q = 334000 J = 334 kJ, with the temperature staying at 0 C. Vaporizing 1 kg of water (L = 2260000 J/kg) takes 2260000 J = 2.26 MJ. Vaporizing 2 kg takes 4520000 J = 4.52 MJ, about 1.25556 kWh or 1080.31 kcal.
Which latent heat values does the calculator use?
Presets: ice fusion 334000 J/kg (0 C) and water vaporization 2260000 J/kg (100 C). You can also enter any custom latent heat in J/kg, kJ/kg, or MJ/kg, for example the fusion or vaporization value of another substance from a reference table.
How do I calculate thermal energy from power and time?
Use Q = P times t. A 2 kW heater running 30 minutes delivers Q = 2000 times 1800 = 3600000 J = 3.6 MJ = exactly 1 kWh, about 860.421 kcal or 3412.14 BTU. The solver also works in reverse: 7200 J delivered at 200 W takes t = 7200 / 200 = 36 s, and 3600000 J over 1 hour means P = 1000 W = 1 kW.
Which units are supported?
Energy: J, kJ, MJ, cal, kcal, BTU, kWh. Mass: kg, g. Time: s, min, h, day. Power: W, kW, MW. Key conversions: 1 kWh = 3600000 J, 1 BTU = 1055.05585 J, 1 cal = 4.184 J, 1 MJ = 1000 kJ. Note: delta-T is entered in K or degrees C, which are identical for a temperature difference.
Is this the same as thermal conductivity or heat transfer rate?
No. This tool computes total thermal ENERGY in joules: how much energy a mass holds, gains, or loses. Thermal conductivity (W/m K) and heat transfer describe the RATE at which heat flows, a different question answered by dedicated heat-transfer tools. Use this calculator for energy content, not for how fast a wall or pipe conducts heat.
How is this different from the joule-heating calculator?
The joule-heating calculator handles ELECTRIC heating: power from current through a resistance (P = I squared R). This thermal-energy calculator handles the energy of a MASS: heating water or metal (Q = m c delta-T), melting and boiling (Q = m L), or energy from any power source over time (Q = P t), with no current or resistance involved.
Why does the calculator reject negative or zero values?
Negative mass, time, energy, or temperature rise are not physical, so the tool errors instead of producing a misleading result. Zero is rejected in the inverse solves (for example delta-T = Q / (m times c)) because it would mean division by zero; solving FOR the energy itself with a zero input is fine and returns 0.