BTU Calculator for a 20×20 Room
A 20×20 room is 400 sq ft. Estimate the cooling BTU and the right AC size here, with climate and sun adjustments.
Runs locally in your browser — no upload, no trackingTry: Room area=400, Ceiling height=8, People usually in room=1, Room type=living, Sun exposure=avg, Insulation quality=avg, Climate zone (1–5)=3 → 8,000 BTU, 0.67 ton, 8,000 BTU window unit, 14,000 BTU
How to use
A 20×20 room is 400 square feet. At the common rule of 20 BTU per square foot, the base cooling load is about 8,000 BTU before people, sun and climate are added. A 20×20 living room or open bedroom is large for a single window unit. Look at 10,000–12,000 BTU, or consider two units for even cooling. Use the calculator to fold in your real ceiling height, insulation and climate zone.
FAQ
What size AC for a 20×20 room?
Start from about 8,000 BTU and adjust upward for sunny windows, poor insulation or a hot climate, and downward for a shaded, tight room. Most 20×20 rooms land near a 5,000–12,000 BTU unit depending on those factors.