🏠What does every room in the house need?

✓ Tested & verified Updated: Aug 9, 2026 How we calculate this

Sizing one room takes a minute. Sizing eight of them and remembering which was which is what a sheet is for.

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How this works

Enter each room as its own row. The tool multiplies floor area by the rate per square foot and scales it by ceiling height over eight feet, then totals every room. Use the per-room figures to choose mini split head sizes or to decide which rooms need their own zone; use the total only as an upper bound for a central system, because summing rooms always overstates a whole-house load.

Cooling load room by room

The base rate before corrections, for the rooms a typical house is made of.

Room	Typical size	Cooling load
Bedroom	12 × 14 ft	3,360 BTU/h
Living room	16 × 20 ft	6,400 BTU/h
Kitchen	12 × 12 ft	6,880 BTU/h
Home office	10 × 10 ft	2,000 BTU/h
Open-plan floor	20 × 30 ft	12,000 BTU/h

Adding room loads gives a larger figure than a whole-house calculation, because no two rooms peak at the same hour. Use it for zoning decisions, not for buying one central unit.

Frequently asked questions

Why is the total higher than a whole-house calculation?

Because rooms peak at different hours. West-facing rooms peak at five in the afternoon and east-facing ones before lunch, so no central system ever has to serve every room at its own maximum. Adding room loads typically overstates by fifteen to twenty-five percent.

What rate should I use per room?

Twenty BTU per hour per square foot is the standard starting point. Raise it for a kitchen, a very sunny room or poor insulation; lower it for a shaded, well-sealed room. Keeping the rate as a column is deliberate — it lets one sheet carry several kinds of room.

Can I use it for heating?

Yes, by putting your climate zone heating rate in the rate column instead — 27 BTU per hour per square foot in zone 1 up to 57 in zone 7. The arithmetic is the same; only the rate changes.

How we calculate this

Each row is length × width × rate × (ceiling ÷ 8). Rows are summed before rounding, so the total never drifts from the sum of the displayed rows. Conversions use 12,000 BTU/h per ton and 3,412.142 BTU/h per kilowatt. The diversity note applies a flat twenty percent, which is the middle of the usual range and a guide rather than a calculation.