HVAC & Energy

AC Tonnage & BTU Cooling Load Calculator

Size your central air conditioning or heat pump unit accurately. Avoid short-cycling from oversized units or high energy bills from undersized compressors.

Recommended AC Unit Size 3.5 Tons of Cooling (Residential)
Required Cooling Load 42,000 BTU/hr 12,000 BTU per Ton of capacity
Standard Equipment Size 3.5 Ton Split System Sized in 0.5-ton increments
Required Blower Airflow 1,400 CFM Standard 400 CFM per Ton of cooling
Estimated Replacement Cost $6,200 – $8,500 Equipment + professional installation
💡 HVAC Pro Warning on Oversizing: Bigger is NOT better in air conditioning. An oversized AC cools a home so quickly that it short-cycles before removing indoor humidity, leaving rooms feeling cold, clammy, and prone to mold growth.
📐 US Climate Zones & Residential Cooling Load Matrix ACCA Manual J / DOE
Zone 1 (Deep South) FL, South TX, Gulf 35-40 BTU / sq ft High Latent Humidity Load Zone 2 (Southwest) AZ, NV, SoCal, NM 30-35 BTU / sq ft Extreme Sensible Heat & Solar Gain Zone 3 (Central) NC, TN, OK, MO, VA 25-30 BTU / sq ft Moderate Summer Heating/Cooling Mix Zone 4 (Midwest) PA, OH, IL, IN, NJ 20-25 BTU / sq ft Moderate Peak Standard Insulation Zone 5 (Northern) NY, MI, MN, WI, WA 15-20 BTU / sq ft Mild Summer Heating Dominant
Zone 1: Subtropical High Humidity
Zone 2: Arid Desert High Solar
Zone 3: Mixed-Humid Central
Zone 4: Temperate Midwest
Zone 5: Cool Northern

How Central AC Tonnage Is Calculated (ACCA Manual J Standards)

One "Ton" of air conditioning has nothing to do with the physical weight of the outdoor condenser. It refers to the cooling power required to melt one ton (2,000 lbs) of ice in 24 hours. In engineering terms:

1 Ton of AC Capacity = 12,000 BTU / hour (British Thermal Units)

Standard Residential AC Sizing by Square Footage

Home Size (Sq Ft) Tonnage (Moderate Zones) Tonnage (Hot Sunbelt Zones) BTU Capacity
600 – 1,000 sq ft1.5 Tons2.0 Tons18,000 – 24,000 BTU
1,000 – 1,400 sq ft2.0 – 2.5 Tons2.5 – 3.0 Tons24,000 – 30,000 BTU
1,400 – 1,800 sq ft2.5 – 3.0 Tons3.0 – 3.5 Tons30,000 – 36,000 BTU
1,800 – 2,300 sq ft3.0 – 3.5 Tons3.5 – 4.0 Tons36,000 – 42,000 BTU
2,300 – 2,800 sq ft3.5 – 4.0 Tons4.0 – 5.0 Tons42,000 – 48,000 BTU
2,800+ sq ftDual-Zone System (e.g. 2.5T + 2.5T)Dual-Zone System (3.0T + 3.0T)60,000+ BTU