How many BTUs do I need for my room size?

Q: How many BTU do I need to cool a 1,000 sq ft house?

A rough rule is 20–25 BTU/hr per square foot, so a 1,000 sq ft home lands around 20,000–24,000 BTU/hr, or about 1.5–2 tons. Hot climates, lots of west-facing glass, or poor insulation push it higher. This is a starting estimate only — an oversized AC short-cycles and will not dehumidify, so confirm with a Manual J load calculation.

Q: Is it bad to oversize an air conditioner?

Yes. An oversized AC cools the air quickly but shuts off before it removes enough humidity, leaving the house cold and clammy and short-cycling the compressor (which shortens its life and wastes energy). Right-sizing from a Manual J load calc — not from square-footage rules of thumb — gives longer run times and far better comfort and dehumidification.

Q: How many square feet does a 2-ton AC cool?

A 2-ton (24,000 BTU/hr) unit typically cools roughly 900–1,300 sq ft in a moderate climate with average insulation. The range is wide because ceiling height, window area, sun exposure, and air-sealing all shift the load — use it as a sanity check against a Manual J result, not as the basis for selecting equipment.

Q: AC tonnage and cooling capacity calculator

This calculator converts a room or home's cooling load into both BTU/hr and tons, where 12,000 BTU/hr equals 1 ton. Enter the conditioned area, climate, insulation, and internal gains and it returns the required capacity so you can round to the nearest standard size (1.5, 2, 2.5 tons…). Confirm with a full Manual J before buying equipment.

Question

How many BTUs do I need for my room size?

Accepted Answer

A quick starting point is 20–25 BTU/hr per square foot of conditioned space, so a 400 sq ft room lands around 8,000–10,000 BTU/hr. Sun exposure, ceiling height, insulation, and the number of occupants all shift that up or down. Enter your room details into the calculator for a Manual J-style estimate — an oversized unit short-cycles and will not dehumidify.