Room size → BTU, tonnage & unit type
Short answer
A 20 × 24 room (480 sq ft) needs about 9,600 BTU of cooling in a temperate climate — round up to a 10,000 BTU (under 1 ton) unit. A window unit or single-zone mini-split is the typical fit; a very sunny, poorly insulated, or hot-climate room of this size can need noticeably more.
Floor area
480 sq ft
Cooling needed
9,600 BTU
Recommended unit
10,000 BTU
Tonnage
0.8 ton
A 20 × 24 room is 480 square feet. At the ENERGY STAR baseline of roughly 20 BTU per square foot, that is about 9,600 BTU of cooling in a temperate climate with average insulation and an 8-ft ceiling. Round up to the next standard size — 10,000 BTU (0.8 ton) — so you are not undersized on the hottest days.
The best unit type here is a window unit or single-zone mini-split. Sun, poor insulation, high ceilings, extra occupants, or a hot climate all push the number up — the calculator below adjusts for your exact room.
This page assumes temperate, average conditions. Open the calculator with a 20 × 24 room pre-filled, then set your climate, insulation, sun, and ceiling height.
Size a 20 × 24 roomReal, widely available units in the Up to 12,000 BTU class. Independent picks — we're not affiliated with any manufacturer or retailer and earn nothing from these links. Always match the unit's BTU to the size above.
Best overall
8,000–12,000 BTU
Window · inverter · U-shape · ~36 dBA · window still opens
The U-shape puts the compressor outside the glass, so it runs about as quiet as a whisper and you can still open the window. Inverter compressor sips power.
Find on AmazonQuietest
8,000–14,000 BTU
Window · dual inverter · Dual-inverter · Wi-Fi · very quiet
LG’s dual-inverter compressor ramps up and down instead of cycling on/off — quieter, steadier temps, and lower running cost than a fixed-speed unit.
Find on AmazonBudget pick
5,000 BTU
Window · fixed-speed · Cheapest way to cool a small room
A no-frills window unit that reliably cools a small bedroom, office, or dorm up to ~150 sq ft for the lowest upfront cost.
Find on AmazonBest value
8,000–12,000 BTU (SACC)
Portable · inverter · No permanent mount · inverter
When a window mount isn’t an option, this inverter portable is one of the few that actually cools like its rating instead of falling short.
Find on AmazonA 20 × 24 room is 480 sq ft, which needs about 9,600 BTU of cooling in a temperate climate at the ~20 BTU/sq-ft baseline. Round up to a standard 10,000 BTU unit so you are not undersized on the hottest days.
A 10,000 BTU unit (0.8 ton). The typical choice is a window unit or single-zone mini-split, or a portable ac as an alternative.
Strong sun (+10%), poor insulation (+15%), ceilings over 8 ft, extra occupants (+600 BTU each beyond two), a kitchen (+4,000 BTU), or a hot climate (+25%) all raise the load. Run your exact room through the calculator to see the adjusted number.