Window U Factor Heat Loss Calculator
Calculate heat loss through windows from U-value, area and indoor-outdoor temperature difference.
Compare Your Options And Get Clear Answers
Calculate heat loss through windows from U-value, area and indoor-outdoor temperature difference.
Window U Factor Heat Loss Estimator
Enter your numbers below for an instant estimate.
How It Works
Key concepts behind this calculator
Enter Values
Fill in each field with your own numbers.
Calculate
Results update as you change the inputs.
Review
Read the breakdown and the explanation.
Adjust
Change values to compare scenarios.
Window Quick Guide
Typical values for reference.
| U-value | Area m2 | Outside °C | Heat loss W |
|---|---|---|---|
| 5 | 12 | 0 | 1,200 W |
| 2.8 | 12 | 0 | 672 W |
| 1.6 | 12 | 0 | 384 W |
| 0.8 | 12 | 0 | 192 W |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Window U Factor Calculator FAQ
Answers to common questions about this calculator.
The rate of heat transfer through a material, in W/m2K.
Triple glazing, about 0.8 to 1.0.
Heat loss = U x area x temperature difference.
It is an estimate based on the inputs you enter. Check real quotes, labels or official guidance for important decisions.