AC Tonnage Calculator & BTU Calculator for Room Size

To calculate AC tonnage for room size: 1) Measure room length × width to get square footage, 2) Use the basic rule of 20-25 BTU per square foot, 3) Add 600 BTU per person, 4) Adjust for climate, insulation, and sun exposure, 5) Divide total BTU by 12,000 to get tonnage. Our AC tonnage calculator automates this process for accurate results.

BTU requirements by room size: 150 sq ft = 5,000 BTU (0.4 tons), 250 sq ft = 6,000 BTU (0.5 tons), 350 sq ft = 8,000 BTU (0.7 tons), 450 sq ft = 10,000 BTU (0.8 tons), 550 sq ft = 12,000 BTU (1 ton), 700 sq ft = 14,000 BTU (1.2 tons), 1,000 sq ft = 18,000 BTU (1.5 tons). These are baseline calculations before environmental adjustments.

Climate significantly impacts AC sizing: Hot climates (90°F+) require 30% more capacity due to higher ambient temperatures and increased cooling demand. Moderate climates (70-90°F) use standard calculations. Cool climates (below 70°F) may require 20% less capacity. Humidity levels, seasonal temperature variations, and regional weather patterns all influence optimal air conditioner sizing.

Key HVAC load factors include: Insulation quality (poor insulation increases load by 25%), sun exposure (south/west-facing rooms need 15% more capacity), ceiling height (high ceilings increase cooling requirements), number of occupants (600 BTU per person), heat-generating appliances, windows and doors, air leakage, and local climate conditions. Professional Manual J calculations consider all these variables for precise sizing.

Undersized AC units run continuously, struggle to cool effectively, increase energy costs, wear out faster, and can’t maintain comfortable humidity. Oversized units short cycle, waste energy, provide poor humidity control, cause temperature swings, and have higher upfront costs. Proper AC sizing ensures optimal efficiency, comfort, and system longevity. Use our calculator for accurate sizing guidance.

Our AC tonnage calculator provides 85-90% accuracy for residential applications using industry-standard Manual J principles. It’s excellent for preliminary sizing and budget planning. Professional HVAC assessments consider additional factors like ductwork design, local building codes, specific equipment efficiency, and detailed heat loss/gain analysis. For optimal results, use our calculator for initial sizing, then consult HVAC professionals for final installation decisions.

SEER rating selection depends on climate and usage: Minimum 13-14 SEER for basic efficiency and lower upfront costs. 15-16 SEER offers good balance of efficiency and affordability for most climates. 17+ SEER provides maximum energy savings in hot climates with high usage. Higher SEER units cost more initially but save significantly on operating costs over 10-15 year lifespan. Consider local utility rebates when selecting high-efficiency models.

This calculator is optimized for residential applications up to 2,000 sq ft. Commercial spaces require specialized calculations considering: higher occupancy loads, commercial equipment heat generation, different ventilation requirements, building codes, and complex zoning needs. For commercial HVAC sizing, consult professional engineers who perform detailed Manual N commercial load calculations and consider specific business requirements.