HVAC Calculators
Size your air conditioner, heat pump, or furnace correctly with our free HVAC calculators. Get BTU, tonnage, and load estimates in seconds — no account, no cost.
BTU Calculator
Room size to required cooling/heating BTU with ceiling, sun, people, and kitchen adjustments.
AC Tonnage Calculator
Convert room square footage to the right air conditioner size in tons, with common unit recommendations.
HVAC Load Calculator
Simplified heating & cooling load estimate based on floor area, windows, people, and sun exposure.
Furnace Size Calculator
What size furnace do I need? Output BTU by home area, climate zone, and insulation.
Mini Split Size Calculator
Recommended mini split BTU and tonnage (9k, 12k, 18k, 24k) for rooms and houses.
Why Use an HVAC Sizing Calculator?
An undersized air conditioner runs non-stop and never cools your home. An oversized one short-cycles, wastes energy, and fails to remove humidity. HVAC sizing calculators give you a fast, reliable estimate before you buy — so you can talk to a contractor with real numbers, or pick the right unit yourself.
These calculators use the same simplified rules of thumb that HVAC pros use for quick estimates: roughly 20–30 BTU per square foot, adjusted for ceiling height, sun exposure, people, and kitchen load. For a precise result, a full Manual J load calculation is still the professional standard — use these tools to get in the right ballpark first.
How HVAC Sizing Works
- Measure your space. Room length × width in feet gives square footage.
- Apply BTU per square foot. Cooling typically needs 20–25 BTU/ft²; add more for hot climates.
- Adjust for your situation. High ceilings, sun-facing walls, extra people, and kitchens all add load.
- Convert to tons. For AC units, divide total BTU by 12,000 (1 ton = 12,000 BTU).
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