HVAC Calculators
Size your HVAC system with engineering-grade calculators
15 articles
Calculators
AC Tonnage Calculator
Here's the deal: both could be right, or both could be wrong. AC tonnage depends on far more than square footage alone.
Air Changes Per Hour Calculator (ACH Formula)
Great question. Air changes per hour (ACH) tells you how many times the entire volume of air in a room is replaced in one hour.
Bathroom Exhaust Fan CFM Calculator
No — that's way undersized.
Ceiling Fan Size Guide
It absolutely matters — and you're asking the right question.
CFM Calculator
We get this kind of question all the time.
CFM Duct Sizing Chart & Calculator
Complete CFM duct sizing charts for rigid and flex duct, plus a calculator for supply and return duct sizing. ACCA Manual D methodology explained with worked examples.
Furnace Sizing Calculator
Furnace sizing calculator using ACCA Manual J methodology. Get the right BTU output for your home from climate zone, square footage, and insulation.
What Size Generator Do I Need
That moment of confusion is exactly why most people either buy a generator that's too small — and trip the overload breaker the first time they plug.
Heat Pump Sizing Calculator
Heat pumps are sized differently than furnaces or air conditioners. A furnace only heats. An AC only cools.
Heating BTU Calculator
Heating BTU Calculator --- How Many BTU To Heat Your Home
Heating Cost Per Square Foot Calculator
Heating cost calculator comparing electric, natural gas, propane, oil, and heat pump systems. Estimate monthly winter heating bills for your home.
How Many BTU Air Conditioner Do I Need
How many BTU your room AC needs. Calculate window or portable AC cooling capacity from room size, climate zone, sun exposure, and ceiling height.
Mini Split Sizing Calculator
Mini split sizing made simple. Calculate required BTU for ductless heat pumps based on room size, climate zone, insulation, and zone count.
What Size Tankless Water Heater Do I Need
If you've started shopping for a tankless water heater, you already know the sizing confusion is real.