Heat Loss Calculator

W/m²K
Well-insulated wall≈0.3, Window≈2.0, Uninsulated wall≈1.0
°C
°C
Construction Updated 16 Jun 2026

Heat Loss Calculator is a construction estimator that helps you calculate heat loss values from your input data. The formula used is: HeatLoss (W) = Area × U-Value × (T_indoor − T_outdoor). Accepts imperial (feet, inches) or metric (metres, cm) units as labelled on each input.

Formula

HeatLoss (W) = Area × U-Value × (T_indoor − T_outdoor)

Example Calculation

Inputs
  • Surface Area: 100
  • U-Value: 0.3 W/m²K
  • Indoor Temperature: 21 °C
  • Outdoor Temperature: 0 °C

Suppose you enter: Surface Area = 100, U-Value = 0.3, Indoor Temperature = 21, Outdoor Temperature = 0. The calculator applies the formula (HeatLoss (W) = Area × U-Value × (T_indoor − T_outdoor)) and shows all output values below. Change any input field to immediately see how the result changes.

Frequently asked questions

What is the Heat Loss?
The Heat Loss Calculator is a construction estimator that helps you calculate heat loss values from your input data. Accepts imperial (feet, inches) or metric (metres, cm) units as labelled on each input.
When should I use this calculator?
Use this calculator whenever you need a quick, accurate result for heat loss values from your input data without working through the arithmetic manually.
What units should I enter?
Accepts imperial (feet, inches) or metric (metres, cm) units as labelled on each input.
How accurate are the results?
Provides material and dimension estimates. Actual quantities depend on site conditions, waste, and cutting losses.
How do I interpret the result?
Always add a 10–15 % buffer to material estimates to account for waste, cutting errors, and variations in workmanship.
How can I verify the calculation manually?
Use the displayed formula and work through the numbers step by step. If your manual result differs slightly, check rounding and unit conversions first.
Can I use this for planning and budgeting?
Yes. Run best-case, expected, and worst-case inputs to compare outcomes and make safer planning decisions.