Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Steady planar conduction using a supplied whole-assembly U-value. Ventilation, thermal bridges, solar gains and heat capacity are excluded.
Example Calculation
- Area: 20 m²
- U-value: 0.5 W/(m²·K)
- Temperature difference: 20 K
20 m² with U=0.5 and a 20 K difference loses 200 W by conduction.
Frequently asked questions
How do I use this calculator?
Enter area, u-value, temperature difference. The result updates automatically. Use Reset to restore the example values.
What method does it use?
heat flow=U × area × temperature difference.. Steady planar conduction using a supplied whole-assembly U-value. Ventilation, thermal bridges, solar gains and heat capacity are excluded.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.