About HVAC Size Calc

HVACSizeCalc was built for homeowners who are tired of getting wildly different quotes from contractors and having no way to verify whether a recommended system is actually the right size. Oversized and undersized HVAC systems are the number one source of comfort complaints, high energy bills, and premature equipment failure in American homes. Our calculators put the sizing math in your hands before you ever talk to a contractor.

What We Cover

• BTU Calculator — Calculate the heating and cooling load for any room or whole house
• HVAC System Size Calculator — Determine the correct tonnage for your home based on square footage, climate zone, insulation, and window area
• Ductwork Size Calculator — Size supply and return ducts for proper airflow
• SEER Savings Calculator — Estimate annual energy savings from upgrading to a higher-efficiency unit
• Heating Cost Calculator — Compare operating costs across gas, electric, and heat pump systems

About the Author: Derek Holloway

Derek Holloway spent fifteen years in the field as an HVAC technician and service manager, working on everything from residential split systems to commercial rooftop units across the mid-Atlantic region. He holds an EPA 608 Universal certification and completed coursework in residential load calculation through ACCA (Air Conditioning Contractors of America), the organization responsible for the Manual J methodology that the industry relies on for proper sizing.

After a back injury pushed him out of the field, Derek turned to writing and consulting. He noticed that homeowners were almost always at a complete information disadvantage when shopping for HVAC equipment — contractors knew the sizing formulas and customers did not. HVACSizeCalc was his answer to that imbalance: give homeowners enough knowledge to have an informed conversation and spot obvious mismatches before signing any contract.

Derek is based in northern Virginia. When he is not writing about HVAC systems, he volunteers as a home energy advisor for a local nonprofit that helps low-income families reduce their utility bills through weatherization and equipment upgrades.

“A system that's the wrong size will cause you problems every day it runs. Getting sizing right is the most important decision in any HVAC project.” — Derek Holloway

Disclaimer

The calculators on HVACSizeCalc provide estimates based on simplified sizing methods for general informational purposes. Accurate load calculations for equipment selection require a full Manual J analysis performed by a qualified HVAC professional using actual building measurements, insulation values, window specifications, and local climate data. Our results should be used to educate yourself, not to finalize equipment purchases. Always consult a HVAC writer contractor before installing or replacing any heating or cooling system.

Affiliate Disclosure

HVACSizeCalc may earn a commission when you click on links to HVAC products, contractors, or related services. These relationships do not affect our calculator methodology or content. We do not recommend specific equipment brands or contractors in exchange for compensation.