Ac Size Calculator
Free Ac size tool for home. Enter your details to get instant, tailored results and guidance. Get results you can export or share.
Formula
BTU = Sq Ft × 20 × Ceiling Factor × Sun Factor × Insulation Factor × Climate Factor
Start with 20 BTU per square foot as the base. Adjust upward for ceilings above 8 feet, heavy sun exposure, poor insulation, and hot/humid climates. Adjust downward for shaded rooms, good insulation, and cool climates. The suggested unit size rounds up to the nearest standard AC size. Monthly running cost assumes 8 hours/day at $0.13/kWh with an EER of 10.
Worked Examples
Example 1: Standard Bedroom
Problem: 350 sq ft bedroom, 8 ft ceilings, average sun exposure, average insulation, moderate climate.
Solution: Base BTU: 350 × 20 = 7,000\nSun adjustment: ×1.0 = 7,000\nInsulation: ×1.0 = 7,000\nClimate: ×1.0 = 7,000\nSuggested unit: 8,000 BTU (next standard size up)\nTon equivalent: 0.58 tons
Result: 7,000 BTU needed | 8,000 BTU suggested unit
Example 2: Large Living Room in Hot Climate
Problem: 600 sq ft living room, 10 ft ceilings, heavy sun, poor insulation, hot climate.
Solution: Base BTU: 600 × 20 = 12,000\nCeiling (10/8): × 1.25 = 15,000\nHeavy sun: × 1.15 = 17,250\nPoor insulation: × 1.2 = 20,700\nHot climate: × 1.2 = 24,840\nSuggested: 24,000 BTU (2 ton unit)
Result: 24,840 BTU needed | 24,000 BTU (2 ton) unit
Frequently Asked Questions
What formula does Ac Size Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
Can I use the results for professional or academic purposes?
You may use the results for reference and educational purposes. For professional reports, academic papers, or critical decisions, we recommend verifying outputs against peer-reviewed sources or consulting a qualified expert in the relevant field.
Can I use Ac Size Calculator on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
Can I share or bookmark my calculation?
You can bookmark the calculator page in your browser. Many calculators also display a shareable result summary you can copy. The page URL stays the same so returning to it will bring you back to the same tool.
Does Ac Size Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.