⚙️ Boiler Size Calculator
Calculate the right boiler size (BTU) for your home
Total heated area of your home
For radiator heating systems
How to Use This Calculator
Enter Home Square Footage
Input the total heated square footage of your home. This is the area that needs heating, excluding unheated spaces like garages.
Enter Ceiling Height
Input the average ceiling height in feet (standard is 9 feet). Higher ceilings require more heating capacity.
Select Climate and Insulation
Choose your climate zone (cold, moderate, warm) and insulation quality (poor, average, good). These factors significantly affect heating requirements.
Select Boiler Type
Choose your boiler type (gas, oil, electric). Different boiler types have different efficiency and cost characteristics.
Calculate and Review
Click "Calculate Boiler Size" to see recommended BTU, closest standard size, and estimated cost. Consult an HVAC professional for accurate sizing.
Formula
BTU per sq ft = Base BTU (varies by climate and insulation)
Base BTU = Square Footage × BTU per sq ft
Adjusted BTU = Base BTU × (Ceiling Height ÷ 9) × Radiator Factor
Recommended BTU = Round up to nearest 5,000 BTU
kW = BTU ÷ 3,412 (1 kW = 3,412 BTU/hr)
Example 1: Moderate Climate, Average Insulation (2000 sq ft, 9 ft ceilings)
Step 1: BTU per sq ft: 40 BTU/sq ft (moderate climate, average insulation)
Step 2: Base BTU: 2000 × 40 = 80,000 BTU
Step 3: Adjusted for ceiling: 80,000 × (9/9) = 80,000 BTU
Step 4: Round up: 80,000 BTU (recommended size)
Step 5: Convert to kW: 80,000 ÷ 3,412 = 23.4 kW
Example 2: Cold Climate, Poor Insulation (2500 sq ft, 10 ft ceilings, 12 radiators)
Step 1: BTU per sq ft: 55 BTU/sq ft (cold climate, poor insulation)
Step 2: Base BTU: 2500 × 55 = 137,500 BTU
Step 3: Adjusted for ceiling: 137,500 × (10/9) = 152,778 BTU
Step 4: Adjusted for radiators: 152,778 × 1.6 = 244,444 BTU
Step 5: Round up: 245,000 BTU (recommended size)
About Boiler Size Calculator
The Boiler Size Calculator is an essential tool for homeowners, contractors, and HVAC professionals who need to determine the right boiler size (BTU) for home heating. This calculator eliminates guesswork by providing precise boiler sizing calculations based on square footage, ceiling height, climate zone, insulation quality, radiators, and boiler type, helping you select the right boiler size for efficient and effective heating.
When to Use This Calculator
- New Boiler Installation: Calculate boiler size needed for new boiler installations
- Boiler Replacement: Determine correct boiler size when replacing existing boiler
- Home Addition: Calculate additional heating capacity needed for home additions
- Budget Planning: Estimate boiler costs based on required size
- HVAC Planning: Plan HVAC systems for new construction or renovations
Why Use Our Calculator?
- ✅ Accurate Sizing: Precise calculations prevent undersizing or oversizing
- ✅ Multiple Factors: Considers climate, insulation, ceiling height, and radiators
- ✅ Standard Sizes: Recommends closest standard boiler size
- ✅ Multiple Types: Supports gas, oil, and electric boilers
- ✅ Cost Estimation: Provides estimated costs based on boiler size and type
- ✅ Time Savings: Instant calculations eliminate manual math and measurements
Common Applications
New Boiler Installation: Homeowners and contractors installing new boilers use this calculator to determine correct boiler size. Proper sizing ensures efficient heating and energy savings while preventing undersizing or oversizing.
Boiler Replacement: Homeowners replacing existing boilers use this tool to verify or recalculate boiler size. Home improvements like better insulation may allow for smaller boilers, while additions may require larger boilers.
Budget Planning: Homeowners and contractors use this calculator to estimate boiler costs based on required size, helping plan budgets and compare options.
Tips for Best Results
- Measure Accurately: Measure heated square footage accurately (exclude unheated spaces)
- Consider All Factors: Account for climate, insulation, ceiling height, and radiators
- Radiator Systems: Include number of radiators for radiator heating systems
- Consult Professional: Always consult an HVAC professional for accurate sizing and installation
- Energy Efficiency: Consider energy-efficient boilers for lower operating costs
- Piping: Ensure piping can handle boiler size
Frequently Asked Questions
What size boiler do I need for a 2000 sq ft home?
For a 2000 sq ft home in a moderate climate with average insulation, you typically need 75,000-85,000 BTU boiler. Actual size depends on climate, insulation, ceiling height, and radiators. Use the calculator with your specific details for accurate sizing.
How many BTUs per square foot do I need for a boiler?
BTU per square foot varies by climate and insulation: 25-35 BTU/sq ft for warm climates, 35-45 BTU/sq ft for moderate climates, and 40-55 BTU/sq ft for cold climates. Better insulation reduces BTU requirements. The calculator adjusts for these factors.
What's the difference between gas, oil, and electric boilers?
Gas boilers are most common and cost-effective. Oil boilers are used where natural gas isn't available. Electric boilers are highly efficient but expensive to operate. The calculator estimates costs differently for each type.
Do I need to include radiators in calculations?
Yes! For radiator heating systems, include the number of radiators. Each radiator adds about 5% to the total heating requirement. The calculator adjusts for radiators automatically.
What are standard boiler sizes?
Standard boiler sizes are typically 50,000, 60,000, 70,000, 80,000, 100,000, 120,000, 140,000, 160,000, 180,000, 200,000, and 250,000 BTU. The calculator recommends the closest standard size to your requirements.
Should I consult a professional?
Yes! While this calculator provides estimates, boiler sizing is complex and requires professional assessment. An HVAC professional considers many additional factors like piping, radiators, hot water needs, and local codes for accurate sizing and installation.