HVAC Size Calculator
Enter the floor area you heat and cool, your climate zone, how well the house is insulated and the ceiling height. The calculator estimates the system size in tons, the heating load and the airflow the ducts must carry.
- Cooling tons
- Heating BTU
- Airflow in CFM
Climate zone 1 is hot, like Florida or Texas. Zone 5 is cold, like Minnesota or Maine.
HVAC systems are sized for the whole house, both summer and winter. Cooling is sold in tons, each 12,000 BTU an hour. In a mixed climate each 500 square feet needs about one ton. Heating needs rise sharply in colder zones, so a heat pump there must be a cold-climate model.
HVAC size chart
Mixed climate, average insulation. Search for a house size.
| Area (sq ft) | Cooling (BTU) | Tons | Heating (BTU) | Airflow (CFM) |
|---|---|---|---|---|
| 1000 | 22500 | 2 | 40000 | 800 |
| 1500 | 33750 | 3 | 60000 | 1200 |
| 2000 | 45000 | 4 | 80000 | 1600 |
| 2500 | 56250 | 5 | 100000 | 2000 |
| 3000 | 67500 | Two systems | 120000 | – |
In a hot climate add about a third to cooling. In a cold one, heating rises by about half.
Floor area and tons
Mixed climate. Slide the floor area.
The outdoor unit is on the right, the furnace and ducts inside.
How to size an HVAC system
Load, then tons. Step through it.
Floor area
Heated and cooled.
Professionals use the ACCA Manual J method, which looks at every window, wall and air leak.
Split system, heat pump or packaged
System types. Compare them.
Separate heating and cooling.
Heats and cools.
All in one box outside.
A heat pump does both jobs with one outdoor unit and can be paired with a furnace as back-up in cold areas.
Before getting quotes
System checks. Tick each item.
Tick each item as you go.
Oversized systems cool quickly but leave the house damp, because they switch off before removing moisture.
What you get
Whole-house sizing. Each tile explains one result.
Cooling size.
BTU an hour.
BTU an hour.
CFM.
Standard or cold.
Each ton of cooling needs about 400 CFM of air. Small ducts make a big system noisy and less efficient.
Frequently Asked Questions
No question matches that search.
What size HVAC system do I need?
In a mixed climate, about one ton of cooling for every 500 square feet, adjusted for insulation and ceiling height.
How many tons for a two thousand square foot house?
About 3.5 to 4 tons in a mixed climate.
How many BTU per square foot for heating?
About 30 in a hot climate up to about 60 in a cold one.
What is a ton in HVAC?
12,000 BTU an hour of cooling.
How much airflow does an HVAC system need?
About 400 cubic feet a minute per ton.
Is a bigger HVAC system better?
No. It short cycles, wastes energy and leaves the air damp.
What is a Manual J calculation?
The industry method for working out a home's heating and cooling load room by room.
Comfort all year
Estimate the cooling tons and heating BTU from your floor area and climate. Then ask for a Manual J load calculation to confirm before you buy.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.