Ensure your room stays warm efficiently with our Heater Size Calculator. By factoring in room dimensions, insulation quality, and your local climate zone, we estimate the heating power (in Watts and BTUs) needed to maintain a comfortable temperature.
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Heater Size Calculator
Estimate Watts & BTUs for heating.
Room & Climate Details
This estimate is for a primary heat source. For supplemental heating (like a space heater), you may need less power. Always choose a heater slightly larger than the calculated requirement.
Calculate Heater Size & Wattage
Calculate the required heater size in Watts and BTUs based on room size and climate.
1
Room Size
Enter length, width, and ceiling height.
2
Climate & Insulation
Select your climate zone and insulation quality.
3
Result
View the recommended Watts and BTUs for your space.
Key Features
Wattage & BTU Output
Get results in both Watts (for electric heaters) and BTUs (for gas/other).
Climate Adjustment
Adapts calculations for Warm, Moderate, or Cold climate zones.
Insulation Factor
Accounts for heat loss based on insulation quality.
Frequently Asked Questions
A general rule is 10 watts per square foot, but this varies significantly with climate and insulation. Our calculator provides a more precise estimate.
Watts measure electrical power, while BTUs measure heat energy. 1 Watt is approximately equal to 3.41 BTUs.
Yes, a larger heater will heat the room faster and cycle off. However, a massively oversized heater might cause temperature swings and waste energy.
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