HVAC Tonnage Calculator
Ballpark HVAC tons from square footage — not a Manual J load calculation. Click any i for detail.
Home size
Conditioned floor area (sq ft)
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Area
Heated/cooled living area, not lot size. |
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Sq ft per ton
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Rule
Common rules of thumb run ~400–600 sq ft/ton depending on climate and insulation. |
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Climate / load factor
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Climate
Use >1 for hotter/humid or poorly insulated homes; <1 for mild climates. |
How to use this calculator
- Enter conditioned square footage.
- Adjust sq ft per ton for your climate rule of thumb.
- Apply a climate factor if needed.
- Have a contractor run Manual J before buying equipment.
Results explained
A crude planning estimate divides floor area by a sq-ft-per-ton rule, then multiplies by a climate factor. Real sizing needs insulation, windows, orientation, infiltration, and local design temperatures (Manual J). Oversized systems short-cycle and dehumidify poorly.
Quick reference: tonnage rules of thumb
tons ≈ (sq ft / sq_ft_per_ton) × climate_factor.
| Item | Detail |
|---|---|
| Mild climate | Often toward 500–600 sq ft/ton |
| Hot / humid | Often toward 400–500 sq ft/ton |
| 1 ton | 12,000 BTU/h cooling |
| Best practice | Manual J + Manual S |
Educational estimate — confirm with a licensed HVAC pro.
How the estimate is built
tons = (sqft / per_ton) × climate_factor.
Example scenario
1,800 sq ft ÷ 500 × 1.0 → 3.6 tons (then pick nearest equipment size with a pro).
FAQ
Is this Manual J?
No. Manual J is a room-by-room load calc. This is a napkin estimate only.
What about heat pumps?
Heating capacity and cold-climate sizing need separate checks beyond this cooling sketch.
Should I round up?
Contractors match available equipment and ducts; blind rounding-up often hurts comfort.
Does ceiling height matter?
Yes in real loads — not modeled here beyond your chosen factor.