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Heating and cooling

Heat Energy Calculator

Use Q = mcΔT to find heat transferred, mass, specific heat capacity, or temperature change. Keep units consistent and distinguish heating from cooling.

Calculate heat energy

Positive heat and temperature change mean heating; negative values mean cooling.

Enter a temperature difference: final minus initial. A change from 20°C to 80°C is +60°C; from 80°C to 20°C is −60°C. A change of 18°F equals 10°C or 10 K.

Mass and specific heat capacity must be positive. Enter the specific heat appropriate to your material and conditions. Grouped numbers such as 1,000.50 are accepted.

Changing an input unit keeps the entered number and clears the previous result. Check the value, then calculate again. Changing the result unit converts an existing result without changing your inputs.

Example: 2 kg × 4,184 J/(kg·K) × 60 K → 502.08 kJ.

Heat transferred

Enter your values to see the result.

Calculated in your browser. Press Enter to calculate. Successful results appear in this tab's Recent calculations.

Three worked examples

Heating

Raise 2 kg by 60°C

Q = m × c × ΔT

With an assumed constant c of 4,184 J/(kg·K), 2 × 4,184 × 60 = 502,080 J, or 502.08 kJ. This is a representative water example, not a universal water property at all temperatures.

Cooling

Cool 500 g by 10°C

Q = 0.5 × 4,184 × (−10)

Using the same assumed c gives −20,920 J. The negative sign means the sample releases 20.92 kJ.

Specific heat

90 J raises 10 g by 20 K

c = Q ÷ (m × ΔT)

90 ÷ (0.01 × 20) = 450 J/(kg·K), or 0.45 J/(g·K).

Formula, units, and limits

Q = mcΔT estimates sensible heat transfer with constant specific heat c and ΔT = final temperature − initial temperature. The SI units are joules, kilograms, and kelvin changes. See OpenStax — Heat Transfer, Specific Heat, and Calorimetry. A measured value for the applicable conditions is preferable to a general material estimate.

A phase change can absorb or release heat without changing temperature. This formula does not include latent heat. It also cannot infer final absolute temperature, a heat-transfer rate, heater electricity consumption, or energy costs from these inputs alone.

Mass conversion uses 1 lb = 0.45359237 kg. Temperature changes use 1 K = 1°C change and 1°F change = 5/9 K. Specific heat conversion uses 1 J/(g·K) = 1,000 J/(kg·K) and 1 thermochemical cal/(g·°C) = 4,184 J/(kg·K). Energy factors follow the Energy Converter, including explicitly labeled thermochemical calories and International Table BTU.

Inputs accept up to 64 characters, 15 integer digits, and 10 decimal places. Units, expressions, and scientific notation belong outside the numeric fields. Hidden fields are ignored. Zero temperature change gives zero heat; inverse calculations with zero temperature change are ambiguous when heat is zero and inconsistent when heat is nonzero.

Arithmetic and unit conversions retain exact integer fractions. Only displayed values round, halfway away from zero, with trailing zeros omitted and ≈ when rounded. A nonzero main result that displays as zero receives a notice. Changing the result unit or precision reuses the unrounded result without adding a history entry.

Common questions

Why is my heat result negative?

For a positive mass and specific heat, a negative temperature change means cooling. The sample releases heat, so Q is negative.

Should I enter 80°C or the change from 20°C to 80°C?

Enter 60 as the temperature change and choose Celsius change. The tool does not subtract initial and final temperatures for you.

Does this calculate boiling, melting, or freezing energy?

No. Q = mcΔT covers a temperature change within a phase. Latent heat is needed for a phase change.

Can I use kWh to estimate an electricity bill?

The kWh result is the sample's heat transfer. Heater efficiency and other losses affect electricity use. Use a separate Electricity Cost Calculator when you know the electrical energy consumed.