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BTU Converter Calculator

BTU Calculator

What is BTU Converter Calculator?

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BTU (British Thermal Unit) measures the amount of energy needed to raise one pound of water by 1°F. For air conditioning and heating, BTU/hr ratings indicate how much thermal energy a system can move per hour. The right BTU capacity prevents under-cooling (too weak) or short-cycling (too powerful).

Calkulon makes complex calculations simple — built for students and everyday problem-solvers.

How to BTU Converter Calculator

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  1. 1Start with 20 BTU per square foot of living space
  2. 2Adjust for ceiling height: multiply by height/8 (standard 8ft ceiling)
  3. 3Factor in climate zone, sun exposure, and number of occupants
  4. 4Add 600 BTU per person beyond two regular occupants

Worked Examples

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Example 1
Given:300 sq ft bedroom, 8ft ceiling, moderate climate
Result:6,000 BTU (0.5 ton)

300 × 20 = 6,000 BTU

Example 2
Given:500 sq ft open plan, 10ft ceilings, sunny
Result:~13,750 BTU (1.1 ton)

Height and sun adjustments add ~37%

Room Size to BTU Guide

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Room Size (sq ft)BTU NeededAC Tons
100–1505,0000.4
150–2506,0000.5
250–3507,0000.6
350–45010,0000.8
450–55012,0001.0
550–70014,0001.2
700–1,00018,0001.5
1,000–1,20021,0001.75
1,200–1,40023,0001.9
1,400–1,50024,0002.0
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Pro Tip

Oversizing is as bad as undersizing. A too-large AC cools fast but cycles off before removing humidity, leaving the room cold and clammy.

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Did you know?

1 ton of air conditioning equals 12,000 BTU/hr — originally derived from the amount of cooling produced by melting one ton of ice over 24 hours.

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Reviewed October 2026
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