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BTU calculator

Estimate a room air-conditioner capacity from floor area, ceiling height, insulation, sunlight, occupants and kitchen use. See every adjustment.

Planning estimate only, based on ENERGY STAR room-air-conditioner size bands and adjustments. Insulation adjustment is your own assumption. Rooms under 100 sq ft use the chart’s 5,000 Btu/h lower-band value; the published chart starts at 100 sq ft. Above 2,500 sq ft, use a professional load calculation. This is not a Manual J calculation or HVAC design. Actual needs depend on climate, windows, air leaks, orientation and building details. Check equipment instructions and consult a qualified HVAC professional.

How many BTUs does my room need?

Measure the room, choose the matching published area band, then adjust for ceiling height, insulation, sunlight, extra occupants and kitchen use. The result rounds up to the next 1,000 Btu/h.

Frequently asked questions

How many BTUs does my room need?

Measure the room, choose the matching published area band, then adjust for ceiling height, insulation, sunlight, extra occupants and kitchen use. The result rounds up to the next 1,000 Btu/h.

Are my room measurements uploaded?

No. The estimate runs in your browser. Room dimensions and assumptions are not sent to a server or saved by this tool.

What does a BTU calculator estimate?

It estimates cooling capacity in Btu per hour for a room air conditioner. This version uses published room-size bands and shows the assumptions added for ceiling height, insulation, sunlight, people and kitchen use.

Can I use this estimate to size central HVAC?

No. It is not a Manual J load calculation or central-system design. Whole-home equipment selection needs climate, windows, insulation, air leakage, orientation, duct and other building data reviewed by a qualified professional.