ApplianceCalc

Air & Comfort

AC BTU Calculator

Estimate room air-conditioner cooling capacity in BTU/h and kW using room dimensions, sunlight, occupancy and insulation.

Guideline-based estimate with empirical adjustments
1

Your appliance details

Units

No sign-up. Your inputs stay in your browser.

2

Your results

Suggested cooling capacity5,000–7,000 BTU/h
Cooling power1.5–2.1 kW
Room area20 m²

What this means

Compare room air conditioners within this approximate range; unusually large or complex rooms need a professional assessment.

Show calculation
  1. ENERGY STAR room-area table provides the baseline capacity.
  2. Adjust baseline by ceiling height ÷ 8 ft, sun factor (0.9 / 1 / 1.1), and estimated insulation factor (0.85 / 1 / 1.2).
  3. Add 600 BTU/h for each occupant above two. Display a ±10% range rounded outward to 1,000 BTU/h.

Important notes

This calculator provides a room air-conditioner sizing estimate and does not replace a professional HVAC load calculation.

Ceiling and insulation adjustments are our empirical allowances. Climate, windows, leakage and kitchen heat can materially change the result.

Calculation basis: Guideline-based estimate with empirical adjustments

Start with room size to narrow the cooling capacities worth investigating. The simplified model adjusts for selected room conditions and shows a range instead of suggesting an exact building heat load. This calculator provides a room air-conditioner sizing estimate and does not replace a professional HVAC load calculation.

How to use

  1. Measure the room dimensions, including the ceiling height.
  2. Enter the usual number of occupants and select the sunlight and insulation descriptions that best fit.
  3. Compare the rounded capacity range with manufacturer sizing guidance for your climate and installation type.

How the calculation works

Formula

Start with the ENERGY STAR floor-area table. Scale ceiling height relative to 8 ft, apply sun factors of 0.9/1/1.1, and add 600 BTU/h per occupant beyond two. Insulation factors of 0.85/1/1.2 are our own empirical adjustments, not ENERGY STAR coefficients. BTU/h ÷ 3,412.14 = kW of cooling.

Example

A 300 ft² room falls near the 7,000–8,000 BTU/h region of the ENERGY STAR room-size table before room-condition adjustments. Strong sun or extra occupants can increase the estimate.

Factors affecting the result

  • Window area, climate, infiltration and heat-generating equipment are not fully modeled.
  • Cooling kW is heat removed, not electrical input kW.
  • An oversized unit can cool quickly without adequately managing humidity.

Frequently asked questions

Is this a Manual J load calculation?

No. Manual J evaluates building construction, climate and detailed heat gains. This is a room-level screening estimate with explicitly approximate adjustments.

Can I use cooling kW to calculate my electric bill?

No. Use measured electricity or the appliance electrical input. Cooling output and electricity input differ because an air conditioner moves heat.

Sources & methodology

Calculation basis: Guideline-based estimate with empirical adjustments. Methodology

Last updated: September 15, 2026