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Heat Transfer Calculator | Conduction & Convection
Thermal Engineering Calculator

Heat Transfer Calculator

Calculate heat transfer rate through conduction, convection, or an overall heat transfer coefficient. Get results in watts, kilowatts, BTU per hour, and total thermal energy.

Enter Heat Transfer Data

Select a calculation method and enter your known values.

°C
°C
m²
W/(m·K)
Example: glass ≈ 0.8 W/(m·K)
m
10 mm equals 0.01 m
Calculate total heat energy over time
hour
Conduction Calculate heat flow through walls, sheets, insulation, and solids.
Convection Estimate heat exchange between a surface and moving fluid.
Overall Transfer Use a known U-value for heat exchangers and composite systems.
Thermal Energy Convert the calculated heat rate into joules or kilowatt-hours.

What Is a Heat Transfer Calculator?

A heat transfer calculator estimates the rate at which thermal energy moves from a hotter region to a colder region. The result is normally expressed in watts, where one watt represents one joule of energy transferred per second.

This calculator supports three common engineering methods: conduction through a solid material, convection between a surface and a fluid, and overall heat transfer using a known U-value.

Conduction Heat Transfer

Conduction occurs when heat moves through a solid material. Common examples include heat passing through a wall, window, metal plate, pipe insulation, or building roof.

The conduction equation used by this tool is: Q̇ = k × A × ΔT ÷ L.

Convection Heat Transfer

Convection describes heat exchange between a surface and a surrounding fluid, such as air, water, steam, or oil. The convection equation is: Q̇ = h × A × ΔT.

Overall Heat Transfer

The overall heat transfer coefficient combines multiple thermal resistances into one value. Engineers commonly use it for heat exchangers, boilers, condensers, insulated systems, and multilayer walls.

The overall equation is: Q̇ = U × A × ΔT.

How the Heat Transfer Calculator Works

  1. Select the transfer method Choose conduction, convection, or overall heat transfer.
  2. Enter both temperatures Provide the hot-side and cold-side temperatures in degrees Celsius.
  3. Add surface and material information Enter area, conductivity, thickness, or the relevant transfer coefficient.
  4. Calculate the thermal result The calculator displays watts, kilowatts, BTU per hour, and optional energy.

Understanding the Calculator Results

The primary result is the heat transfer rate in watts. A positive value represents the magnitude of thermal energy moving from the hotter side toward the colder side.

  • Watts: joules of heat transferred every second.
  • Kilowatts: watts divided by 1,000.
  • BTU/hr: a common thermal unit used in HVAC systems.
  • Joules: total heat transferred during a selected period.
  • kWh: thermal energy expressed in kilowatt-hours.

Actual heat transfer can differ because of radiation, thermal bridges, changing temperatures, surface fouling, airflow variation, moisture, and contact resistance.

Frequently Asked Questions

Important information about heat flow, formulas, units, and calculator accuracy.

The formula depends on the heat transfer mechanism. Conduction uses Q̇ = kAΔT/L, convection uses Q̇ = hAΔT, and overall heat transfer uses Q̇ = UAΔT.

Heat transfer rate measures how quickly thermal energy moves and is expressed in watts. Heat energy is the total amount transferred over time and is expressed in joules or kilowatt-hours.

Yes. Temperature differences have the same numerical value in degrees Celsius and kelvin. A difference of 20°C is equal to a difference of 20 K.

Use the conductivity value for the specific material and operating temperature. Conductivity can change with material composition, density, temperature, and moisture.

The overall coefficient, or U-value, represents the combined effect of conduction, convection, fouling, and other thermal resistances across a complete system.

No. This calculator focuses on conduction, convection, and overall heat transfer equations. Radiation requires surface emissivity and absolute temperatures.

The result is useful for estimates, education, and preliminary analysis. Critical engineering designs should be checked by a qualified professional using verified material and operating data.