# Heat Convection Calculator (Newton's Law, q=hΔT)

Compute convective heat transfer (Newton's law of cooling): heat flux q = h·ΔT (W/m²), heat flow rate Q = h·A·ΔT (W), and convective thermal resistance R_conv = 1/(h·A) (K/W). h is the convective heat-transfer coefficient (W/(m²·K)); ΔT is the temperature difference between the surface and the fluid (K; a °C difference equals a K difference, a °F difference is converted by ×5/9); A the heat-transfer area. ΔT may be negative (indicating reverse heat flow), but h and A must be positive. Area in m²/cm².

> Canonical page: https://elysiatools.com/en/tools/heat-convection-calculator

- **Category:** Math & Numbers

- **Keywords:** heat convection, Newton's law of cooling, convective heat transfer coefficient, heat flux, heat flow rate, convective thermal resistance, convection, heat transfer, surface, fluid, hΔT, thermal

## Overview

The Heat Convection Calculator applies Newton’s law of cooling to calculate heat flux q, heat flow rate Q, and convective thermal resistance from the heat-transfer coefficient, temperature difference, and transfer area.

## Inputs

- **Heat Transfer Coefficient h (W/(m²·K))** (number): Convective heat-transfer coefficient h in W/(m²·K).
- **Temperature Difference ΔT** (number): Temperature difference ΔT between the surface and the fluid, in the selected Temperature Unit. May be negative to indicate the reverse heat-flow direction.
- **Temperature Unit** (select): Unit of the temperature difference. This is a difference, not an absolute temperature: Δ°C = ΔK and Δ°F ×5/9 = ΔK.
- **Heat Transfer Area A** (number): Heat-transfer area A, in the selected Area Unit.
- **Area Unit** (select)
- **Decimal Places** (number)

## When to use

- Estimate convective heat flux from a surface-to-fluid temperature difference.
- Calculate total heat flow through a known heat-transfer area.
- Find convective thermal resistance for thermal design or comparison.

## How it works

- Enter the convective heat-transfer coefficient h in W/(m²·K).
- Enter the temperature difference ΔT and select K, °C, or °F; °F differences are converted to kelvins.
- Enter the heat-transfer area and select m² or cm².
- The calculator returns q = h·ΔT, Q = h·A·ΔT, and R_conv = 1/(h·A) in JSON format.

## Use cases

- Compare natural-air and forced-fluid convection scenarios using different heat-transfer coefficients.
- Estimate heat removal from equipment, panels, or other surfaces with a known area.
- Include convective thermal resistance in a thermal design calculation.

## Frequently asked questions

### What does this calculator calculate?

It calculates heat flux q in W/m², heat flow rate Q in W, and convective thermal resistance R_conv in K/W.

### Which formula is used for heat flux?

Heat flux is calculated with q = h·ΔT.

### Can I enter a temperature difference in Celsius or Fahrenheit?

Yes. A Celsius difference equals the same kelvin difference, while a Fahrenheit difference is converted by multiplying by 5/9.

### Can the temperature difference be negative?

Yes. A negative ΔT indicates heat flow in the reverse direction.

### What values must be positive?

The heat-transfer coefficient h and area A must be positive. The temperature difference may be negative.

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