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Calcimator

BTU / HVAC Sizing Calculator

Calculate the BTU capacity needed for heating and cooling based on room size, insulation, climate, and windows.

Inputs

sq ft
ft

Results

Cooling BTU Needed

11,800

AC Tonnage1
Suggested AC Size1 tons
Furnace BTU12,980
BTU per Sq Ft29.5

Cooling BTU Needed

11,800

How to Use This Calculator
  1. Start by filling in the input fields below. Results update instantly as you type, so you can experiment with different values to see how they affect the outcome.
  2. Room Area — Total floor area of the room or space to condition. Accepts values from 50 sq ft to 10,000 sq ft (default: 400 sq ft).
  3. Ceiling Height — Height of the ceiling in feet. Accepts values from 7 ft to 20 ft (default: 8 ft).
  4. Insulation Quality — Quality of wall and ceiling insulation in the space. Choose from: Poor (old/uninsulated), Average, Good, Excellent (new build). default: 2.
  5. Climate Zone — General climate zone for your location. Choose from: Mild (Pacific NW, coastal), Moderate (Mid-Atlantic), Hot (Southeast, Southwest), Very Hot (Desert, Gulf Coast), Cold (Midwest, Mountain). default: 2.
  6. Number of Windows — Number of windows in the room (adds ~1000 BTU each). Accepts values from 0 to 30 (default: 3).
  7. Once all inputs are set, review your results in the Results panel. Here's what each output means:
  8. Cooling BTU Needed — shown as a numeric value. This is the primary result of this calculator.
  9. AC Tonnage — shown as a numeric value.
  10. Suggested AC Size — shown as a numeric value.
  11. Furnace BTU — shown as a numeric value.
  12. BTU per Sq Ft — shown as a numeric value.
  13. Explore the related calculators below if you need deeper analysis or want to approach this topic from a different angle.
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