AC Size Calculator – What Size AC Do I Need?
Find the right air conditioner size in BTU and tons for your home. Enter your square footage and adjust for climate, ceilings, sun, and occupancy for an accurate estimate.
Rule of thumb: ~20 BTU per sq ft | 12,000 BTU = 1 ton
Air Conditioner Sizing Calculator
+600 BTU per person over 2
This is a Manual J-style estimate for quick planning. For a permit or a new system purchase, have an HVAC contractor run a full Manual J load calculation that also accounts for insulation, windows, and ductwork.
AC Unit Size Chart by Square Footage
As a starting point, a home needs about 1 ton (12,000 BTU) of cooling for every 500–600 sq ft. So a 1,500 sq ft house typically needs a 2.5–3 ton (30,000–36,000 BTU) AC, and a 2,000 sq ft house needs about 3–3.5 tons (36,000–42,000 BTU). Adjust up for hot climates, sunny rooms, high ceilings, or many occupants.
| Home Size | Cooling Capacity | AC Size (Tons) |
|---|---|---|
| 600 – 1,000 sq ft | 18,000 BTU | 1.5 ton |
| 1,000 – 1,500 sq ft | 24,000 BTU | 2 ton |
| 1,500 – 2,000 sq ft | 30,000 BTU | 2.5 ton |
| 2,000 – 2,500 sq ft | 36,000 BTU | 3 ton |
| 2,500 – 3,000 sq ft | 42,000 BTU | 3.5 ton |
| 3,000 – 3,500 sq ft | 48,000 BTU | 4 ton |
| 3,500 – 4,000 sq ft | 60,000 BTU | 5 ton |
Chart assumes a moderate climate and average conditions. Hot southern climates can push each row up by half a ton. Convert any capacity with our tons to BTU and HVAC unit converters.
How to Size an Air Conditioner
Step 1: Base Load
Step 2: Adjustments
• Hot climate: use 23–26 BTU/sq ft
• Very sunny room: add 10%
• Heavily shaded: subtract 10%
• Each person over 2: add 600 BTU
• Kitchen: add 4,000 BTU
• Ceilings over 8 ft: scale up proportionally
Frequently Asked Questions
What size AC does a 2,000 sq ft house need?
A 2,000 sq ft house typically needs a 3 to 3.5 ton AC (36,000–42,000 BTU) in a moderate climate. In hot southern climates, or with lots of sun and high ceilings, size up toward 4 tons (48,000 BTU). In cool northern climates, 3 tons is usually enough.
How many square feet will a 3 ton AC cool?
A 3 ton AC (36,000 BTU) cools roughly 1,500–2,100 sq ft in a moderate climate. The exact area depends on climate, insulation, ceiling height, sun exposure, and how many people use the space.
Is a 3.5 ton enough for 2,000 sq ft?
Yes. A 3.5 ton unit (42,000 BTU) comfortably cools a 2,000 sq ft home in most climates, and is a good choice for hot regions, sunny exposures, or homes with high ceilings where a 3 ton might fall slightly short.
Will a 2 ton unit cool a 1,500 sq ft house?
A 2 ton unit (24,000 BTU) is usually a bit small for 1,500 sq ft — that size is better suited to about 1,000–1,200 sq ft. A 1,500 sq ft home generally needs 2.5 to 3 tons unless it is in a cool climate with excellent insulation and shade.
Is it better to oversize or undersize an AC unit?
Neither — proper sizing is best. If you must choose, err only slightly large. A badly oversized unit short-cycles and leaves the air humid; an undersized unit runs constantly and never quite cools the space. Aim to match the calculated load within about half a ton.
How many sq ft will 20,000 BTU cool?
20,000 BTU (about 1.67 tons) cools roughly 1,000 sq ft in a moderate climate using the ~20 BTU per sq ft rule. For a single room, 20,000 BTU suits a large living room or open area of 800–1,000 sq ft.