HVAC Tonnage Calculator by Square Foot
Rough air conditioner size for a home.
Enter your values
Enter the home area in sq ft.
Choose one of: Cool northern, Mixed, Hot southern, Very hot / desert.
Choose one of: Well insulated / new, Average, Older / leaky.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Estimated load
- 46,800 BTU/h
- Tonnage
- 3.9 tons
- Round to
- 4 tons
- Airflow at 400 CFM/ton
- 1,560 CFM
- Caution
- Confirm with a Manual J before buying
Quick answer
A rough estimate is 20-30 BTU per square foot, but a Manual J load calculation is always more accurate.
tons = area x BTU per sq ft / 12000
At a glance
| What it does | Rough air conditioner size for a home. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Home area, Climate, Insulation |
| Main output | Estimated load |
| Formula | tons = area x BTU per sq ft / 12000 |
| Cost | Free — no sign-up, no download |
How to use the HVAC Tonnage Calculator by Square Foot
- 1Enter conditioned floor area, climate and insulation quality.
- 2Round to the nearest half ton — equipment only comes in those steps.
- 3Get a Manual J load calculation before purchase; oversizing hurts humidity control badly.
Inputs explained
- Home area(sq ft)
- Enter the home area in sq ft.
- Climate
- Choose one of: Cool northern, Mixed, Hot southern, Very hot / desert.
- Insulation
- Choose one of: Well insulated / new, Average, Older / leaky.
Worked example
Using the values the calculator loads with:
Inputs
- Home area1800 sq ft
- ClimateMixed
- InsulationAverage
Results
- Estimated load46,800 BTU/h
- Tonnage3.9 tons
- Round to4 tons
- Airflow at 400 CFM/ton1,560 CFM
- CautionConfirm with a Manual J before buying
Frequently asked questions
Is bigger safer?
No — an oversized system short cycles, leaves the house clammy and wears out faster.
Why does insulation matter so much?
A tight, well-insulated house can need 40% less capacity than an equal-sized leaky one.
What do I need to enter into the HVAC Tonnage Calculator by Square Foot?
Just 3 values: home area, climate, insulation. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the HVAC Tonnage Calculator by Square Foot work out the answer?
A rough estimate is 20-30 BTU per square foot, but a Manual J load calculation is always more accurate. It applies the formula tons = area x BTU per sq ft / 12000 and shows the working so you can check each step by hand.
Is the HVAC Tonnage Calculator by Square Foot free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.