❄️ HVAC Sizing Tool

BTU Calculator

Find the exact BTU rating you need for an air conditioner or heater. Enter your room's measurements and conditions for a precise recommendation.

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Insulation Quality

Sun Exposure

Typical Occupants

Kitchen / High Heat Source?

Climate Zone

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BTUs Required

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Sq Ft

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Tons (HVAC)

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kW Equivalent

📊 BTU Quick Reference Chart

Room Size	BTU Needed	AC Tons	Example Room
100–150 sq ft	5,000–6,000	0.5 ton	Small bedroom, office
150–250 sq ft	6,000–8,000	0.5–0.7 ton	Standard bedroom
250–350 sq ft	8,000–10,000	0.7–0.8 ton	Large bedroom, den
350–550 sq ft	10,000–14,000	1 ton	Studio, small living room
550–700 sq ft	14,000–18,000	1.5 ton	Living room, open plan
700–1,000 sq ft	18,000–22,000	1.5–2 ton	Large living area
1,000–1,400 sq ft	22,000–28,000	2 ton	Open-plan downstairs
1,400–2,000 sq ft	28,000–36,000	2.5–3 ton	Full floor / large home
2,000–2,500 sq ft	36,000–48,000	3–4 ton	Large home

Frequently Asked Questions

What does BTU stand for and what does it mean?

BTU stands for British Thermal Unit — the amount of heat needed to raise one pound of water by 1°F. For AC units, BTU measures how much heat the unit can remove from a room per hour. Higher BTU = more cooling power.

Is bigger always better for AC units?

No — an oversized AC unit is actually worse than a correctly sized one. An oversized unit cools too quickly, never runs long enough to dehumidify properly, and creates uncomfortable temperature swings. It also cycles on/off more frequently, increasing wear and energy use. Size it right.

What's the difference between BTU and tons in HVAC?

In commercial HVAC, capacity is expressed in "tons" — 1 ton = 12,000 BTU per hour. A 2-ton central AC unit = 24,000 BTU. Window units are typically rated in BTU, while central systems use tons. Our calculator shows both.

Does insulation quality really affect BTU needs?

Dramatically. A poorly insulated room can require 30–50% more BTU than a well-insulated one of the same size. Improving insulation and sealing air leaks is often more cost-effective than buying a larger AC unit. Even basic weatherstripping can reduce BTU needs significantly.

Should I use this for central AC sizing?

This calculator is great for room-by-room sizing and window/portable AC units. For central AC or whole-home systems, a licensed HVAC contractor should perform a Manual J load calculation, which accounts for ductwork, the building envelope, and local climate data more precisely.