Inputs
~24,000 BTU / 2.0 ton
Cooling Load
24,000
BTU/hr
2.0 ton AC recommended
Typical Range
2.0–2.5
ton
Equivalent
24.0k
BTU/hr
Equipment Recommendation
Central AC or multi-zone mini-split
How we calculated this
= 24,000 BTU
Rule-of-thumb estimate. For code-compliant sizing, consult a licensed HVAC contractor.
Reference
Quick AC Size Reference Table
Standard estimates for moderate climate, 8 ft ceilings, average insulation. Adjust up 15–25% for hot climates or unusual conditions.
| Home Size (sq ft) | Cooling BTU/hr | Tonnage | Typical Use |
|---|---|---|---|
| 600–900 | 12,000–18,000 | 1–1½ ton | Small home / large condo |
| 900–1,200 | 18,000–24,000 | 1½–2 ton | Condo / small home |
| 1,200–1,500 | 24,000–30,000 | 2–2½ ton | Average home |
| 1,500–2,000 | 30,000–40,000 | 2½–3½ ton | Mid-sized home |
| 2,000–2,500 | 40,000–50,000 | 3½–4 ton | Large home |
| 2,500–3,000 | 50,000–60,000 | 4–5 ton | Very large home |
Learn
Understanding AC Sizing
How many BTUs per square foot?
The industry rule of thumb for whole-home AC sizing is 20 BTU per square foot in a moderate climate. A 1,500 sq ft home needs roughly 30,000 BTU/hr — a 2.5-ton system. This calculator starts from that baseline and adjusts for climate and unusual building conditions.
What does AC tonnage mean?
One ton of cooling equals 12,000 BTU/hr. The unit comes from the era of ice cooling: one ton of ice melting over 24 hours removes exactly that much heat. Contractors quote AC size in tons; equipment spec sheets list both.
Why climate zone matters
Hot-climate homes work against higher outdoor design temperatures and longer cooling seasons. We add 20% capacity for hot zones and reduce it 15% for cold zones, where cooling demand is modest even at peak.
When to size up
Bump capacity for west-facing sunrooms, top-floor units with direct roof exposure, vaulted or 9+ ft ceilings, and rooms with poor insulation. Each adds 10–15% load. Basements and heavily shaded rooms generally need less cooling, not more.
Oversizing vs. undersizing
An undersized AC runs constantly and never reaches setpoint on the hottest days. An oversized AC is worse: it cools the room quickly, shuts off, then short-cycles — never running long enough to dehumidify. The room feels cool but clammy, and the compressor wears out faster. Aim for the recommended tonnage, not a size larger.
FAQ
Common Questions About AC Sizing
How do I calculate what size AC I need?
Start with 20 BTU per square foot of conditioned space, then adjust for climate and unusual conditions. A 1,500 sq ft home in a moderate climate needs about 30,000 BTU/hr — a 2.5-ton AC. This tool runs that math instantly and gives a tonnage range you can shop within.
How many BTUs per square foot for air conditioning?
For whole-home central AC, plan on 20 BTU per sq ft in moderate climates, 24 BTU/sq ft in hot climates, and 17 BTU/sq ft in cold climates. Room-level window units typically use a higher ratio (25 BTU/sq ft) because they account for window and wall losses individually — use the BTU Calculator for single-room sizing.
What does AC tonnage mean?
Tonnage describes cooling capacity, not weight. One ton equals 12,000 BTU/hr of heat removal — derived from how much heat one ton of melting ice absorbs in 24 hours. A 3-ton AC removes 36,000 BTU/hr. Residential central air systems typically range from 1.5 to 5 tons.
Is it better to oversize or undersize an AC?
Neither — right-size it. Undersizing means the system can't reach setpoint on peak days. Oversizing causes short-cycling: the AC blasts cold air, hits setpoint quickly, and shuts off before it can dehumidify. The room feels clammy, the compressor cycles wear it out faster, and energy bills climb. If you must round, round down, not up.
Does a basement need less cooling capacity?
Yes. Basements are below grade, so they exchange heat with cool soil instead of hot outdoor air. They also receive no direct solar gain. We apply a ×0.90 factor for basement-conditioned space. The same logic applies to heavily shaded rooms with mature tree cover.
Related Tools
BTU Calculator
Room-level BTU sizing with windows, walls, insulation, and occupants.
↳ 15×15 room · sunny · 2 windows → 8,000 BTU
HVAC Load Calculator
Whole-home sizing using simplified Manual J methodology.
↳ 2,000 sq ft · mixed climate → 3.5 tons
Furnace Size Calculator
Heating BTU and AFUE efficiency recommendation by climate.
↳ 1,800 sq ft · cold climate → 80,000 BTU