What is thermal resistance?

Thermal resistance (R) measures how strongly a material opposes heat flow. Higher R means better insulation. The formula is R = L / (k × A), where L is thickness (m), k is thermal conductivity (W/m·K), and A is cross-sectional area (m²). Unit: K/W.

What is the difference between series and parallel thermal resistance?

In series (layers stacked in the direction of heat flow), resistances add: R_total = R1 + R2. In parallel (heat can flow through multiple paths side by side), the reciprocals add: 1/R_total = 1/R1 + 1/R2.

What are typical thermal conductivity values?

Copper: ~400 W/m·K; Aluminum: ~205 W/m·K; Steel: ~50 W/m·K; Concrete: ~1.7 W/m·K; Glass: ~1.0 W/m·K; Brick: ~0.7 W/m·K; Wood: ~0.15 W/m·K; Fiberglass insulation: ~0.04 W/m·K; Air: ~0.026 W/m·K.

How do I calculate heat flow from thermal resistance?

Heat flow Q = ΔT / R_total, where ΔT is the temperature difference across the material (in Kelvin or °C) and R_total is the total thermal resistance in K/W.

What is R-value in building insulation?

Building R-value is the thermal resistance per unit area: R_area = L / k (m²·K/W). This tool computes the full R = L/(k·A) by including actual area. To get the per-area R-value, set area to 1 m².

Thermal Resistance Calculator

Name: Thermal Resistance Calculator
Availability: InStock
Author: Nham Vu

Compute thermal resistance for single or multiple material layers in series or parallel configurations.

Material Layers

Configuration:

Results

Enter layer values and click Calculate.

Common Thermal Conductivities (k)

Material	k (W/m·K)

Summary

Compute thermal resistance for single or multiple material layers in series or parallel configurations.

How it works

Enter the thickness (L), thermal conductivity (k), and cross-sectional area (A) for each material layer.
The tool computes R = L / (k × A) for each layer.
Select Series or Parallel configuration to combine multiple layers.
For series: R_total = R1 + R2 + ... For parallel: 1/R_total = 1/R1 + 1/R2 + ...
Read the total thermal resistance and per-layer breakdown in the results panel.

Use cases

Design building walls with insulation, concrete, and drywall layers.
Analyze heat sink performance in electronics cooling.
Compare insulation materials by R-value per unit thickness.
Calculate heat flow through composite pipe walls.
Evaluate window glazing thermal performance.
Size heat exchangers for industrial processes.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu