BTU Calculator
Calculate heating and cooling BTU requirements
Length of the room
Width of the room
Standard: 8 ft
Affects BTU per sq ft
Afternoon sun increases cooling load
Cooling BTU
—
BTU/h
Heating BTU
—
BTU/h
AC Tonnage
—
tons
Heater Wattage
—
watts
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Our BTU calculator helps you size heating and cooling equipment properly. Correct sizing is critical for comfort and efficiency.
- Measure room dimensions
- Assess insulation quality and sun exposure
- Enter specifications
- Use results to select properly sized HVAC equipment
Expert Insights
Smart analysis for your HVAC project
Right-Sizing Analysis
Oversized AC short-cycles and dehumidifies poorly. AI uses Manual J principles to estimate correct tonnage based on your inputs.
SEER Efficiency ROI
16 SEER costs ~15% more than 14 SEER but saves 15-20% annually. AI calculates payback period for each efficiency tier.
Duct Leakage Impact
20-30% energy lost through leaky ducts. AI estimates potential savings from duct sealing based on your home size.
Calculation Formula
Base BTU = Area x 25 (cooling) or x 35 (heating)
Adjustments for ceiling height, insulation, sun exposure
1 ton AC = 12,000 BTU/h
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- Air Conditioning Contractors of America (ACCA) — Manual J — Residential Load Calculation. Learn more
- U.S. Department of Energy — SEER Efficiency Standards. Learn more
- ASHRAE — Standard 55 — Thermal Environmental Conditions for Human Occupancy. Learn more
Frequently Asked Questions
How many BTU per square foot?
Cooling: 20-25 BTU/sq ft. Heating: 30-40 BTU/sq ft. Kitchens and sunrooms need 10-20% more.
What does AC tonnage mean?
One ton = 12,000 BTU/h. A 2-ton unit provides 24,000 BTU/h. Most residential AC units range 1.5-5 tons.
What happens if my AC is oversized?
Oversized units short-cycle, reducing dehumidification, increasing energy bills, and shortening equipment life.