# 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.

Page: https://freecalculator.tech/tools/heat-transfer-calculator
Last reviewed: 2026-11-03

## Formula

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

- 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).

## Inputs

- 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

k = 0.04 W/m·K.
1. Q = 0.04 × 10 × 20 ÷ 0.1.
2. Q = 80 W.

## 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.

### Is radiation included?

No, only if it is already folded into the h or U value you enter.

### Can ΔT be negative?

Yes — a negative result means heat flows the other way.

### 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.

## 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.

## Sources

- OpenStax (Rice University) — https://openstax.org/details/books/university-physics-volume-2

## Cite this page

- APA: Free Calculator. (2026, November 3). Heat Transfer Calculator. https://freecalculator.tech/tools/heat-transfer-calculator
- MLA: "Heat Transfer Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/heat-transfer-calculator.
- Link: Heat Transfer Calculator — Free Calculator, https://freecalculator.tech/tools/heat-transfer-calculator