Heat Transfer Calculator

Calculate heat transfer step by step: Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT.

In short

Formula: Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT.

Heat transfer rate

80 W

BTU/h: 272.9714
Kilowatts: 0.08 kW

What this calculator does

Calculate heat transfer step by step: Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT. Worked example, questions and limitations included.

Use it to turn Mode, k (W/m·K), h (W/m²·K) or U (W/m²·K), Area, Temperature difference, and the other shown inputs into a checked result you can compare, copy, or rerun with different assumptions.

The page shows the formula, a numeric worked example, and the assumptions that affect this thermal & hvac calculation.

Inputs and what they mean

Mode: — choice value.
k (W/m·K), h (W/m²·K) or U (W/m²·K): — number value.
Area: — number value.
Temperature difference: — number value.
Thickness (conduction only): — number value.

How to use it

Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
Check the breakdown to see every intermediate step.
Read the limitations before relying on the result.

Formula

Steady-state, one-dimensional heat flow.

Coefficients are user-entered from material data — none are assumed.

A temperature difference in K equals the same difference in °C.

Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT.

Inputs used: Mode, k (W/m·K), h (W/m²·K) or U (W/m²·K), Area, Temperature difference, Thickness (conduction only).

Worked example

10 m² of 100 mm insulation, ΔT 20 K

Q = 0.04 × 10 × 20 ÷ 0.1.
Q = 80 W.

Reading the result

The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.

Limitations and assumptions

Steady state.
One-dimensional.
Thermal bridges not modelled.
Results are estimates for planning and learning. Real designs, installations and bids must be checked by a qualified, licensed professional against the codes that apply where you work.
The result depends on the values you enter for this heat transfer calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

Common questions

What is a U-value?

The overall heat transfer rate through a building element per m² per kelvin, including all layers and surface films. Check the formula, example, and limitations on this page before using the result for a real thermal & hvac decision.

Is radiation included?

No, only if it is already folded into the h or U value you enter. Check the formula, example, and limitations on this page before using the result for a real thermal & hvac decision.

Can ΔT be negative?

Yes — a negative result means heat flows the other way. Check the formula, example, and limitations on this page before using the result for a real thermal & hvac decision.

How do I use the Heat Transfer Calculator?

Enter the required values for Mode, k (W/m·K), h (W/m²·K) or U (W/m²·K), Area, Temperature difference, Thickness (conduction only). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

What formula does the Heat Transfer Calculator use?

Conduction Q = k A ΔT ÷ L; convection Q = h A ΔT; overall Q = U A ΔT. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.

Can the Heat Transfer Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.