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Air conditioner BTU calculator

Air conditioner size for a room in BTU/h, tons and kW from floor area, ceiling height, insulation, sun and occupants, beside the Energy Star chart.

업데이트 검증한 예제: 4

시도하기
Cooling load
BTU/h
Cooling load: 6,000 BTU/h
정수; 가장 가까운 값, 중간값은 0에서 먼 쪽으로
Cooling load
0.5tons / 1.76kW
Next common unit size
6,000BTU/h
Energy Star chart for this area
8,000BTU/h
This is a rule-of-thumb estimate. For a whole house or an unusual room, a Manual J load calculation is the reliable method.

By the rule of thumb the room needs about 6,000 BTU/h (0.5 tons, 1.76 kW), so look at 6,000 BTU/h units. The Energy Star chart suggests 8,000 BTU/h for the same floor area.

Where the load falls among common unit sizes (BTU/h)

5,000 unit6,000 unit8,000 unit10,000 unit4,0005,0006,0008,00010,000Energy Star chart 8,0006,000 BTU/h
계산 방법 S

  1. Base load (rule of thumb)

    300 ft2×20=6,000 BTU/h300\ \text{ft}^2 \times 20 = 6{,}000\ \text{BTU/h}

    About 20 BTU/h per ft² for an 8 ft ceiling (27.87 m²), this calculator's rule of thumb. The Energy Star chart gives 8,000 BTU/h for this area, 26.7 per ft².

  2. Ceiling height and insulation

    6,000×88×1=6,0006{,}000 \times \frac{8}{8} \times 1 = 6{,}000

    Scaled by room volume; the insulation factors (good 0.9, average 1.0, poor 1.2) are this calculator's assumption.

  3. Sun (Energy Star)

    6,000×1=6,0006{,}000 \times 1 = 6{,}000

  4. People and kitchen (Energy Star)

    +600×0+0=6,000 BTU/h+ 600 \times 0 + 0 = 6{,}000\ \text{BTU/h}

  5. Tons and kilowatts

    6,00012,000=0.5 tons,6,000×0.293071÷1000=1.758426 kW\frac{6{,}000}{12{,}000} = 0.5\ \text{tons},\quad 6{,}000 \times 0.293071 \div 1000 = 1.758426\ \text{kW}

Air conditioner BTU calculator 소개

The cooling load starts at 20 BTU/h per square foot for an 8 ft ceiling, scales with ceiling height and an insulation factor, then takes Energy Star's room air conditioner adjustments: 10% less for a heavily shaded room, 10% more for a very sunny one, 600 BTU/h for each regular occupant beyond two and 4,000 BTU/h for a kitchen. The load is also given in tons (12,000 BTU/h each) and kW, with the next common unit size.

A 300 ft² room with an 8 ft ceiling and average conditions comes to 6,000 BTU/h, half a ton or 1.76 kW. Energy Star's sizing chart, based on 8 ft ceilings, lists 8,000 BTU/h for 300 up to 350 ft², so its figure is shown alongside for rooms of 100 to 2,500 ft².

Both are estimates for one room. For a whole house, ACCA describes its Manual J as the ANSI-recognised method for equipment sizing loads.

계산 예제

300 ft² room, 8 ft ceiling, average everything

방 면적
300 ft²
Ceiling height
8 ft
Insulation
평균
Sun exposure
Normal
People who regularly use the room
2
Cooling load
6,000 BTU/h
Cooling load
0.5 tons
Cooling load
1.76 kW
Next common unit size
6,000 BTU/h
Energy Star chart for this area
8,000 BTU/h

검증 출처: Python decimal: 300 × 20 = 6,000 BTU/h ÷ 12,000 = 0.5 ton × 0.29307 = 1.758 kW; Energy Star chart row 300–350 ft² = 8,000

Sunny 400 ft² kitchen, 10 ft ceiling, poor insulation, 4 people

방 면적
400 ft²
Ceiling height
10 ft
Insulation
Poor
Sun exposure
Very sunny
People who regularly use the room
4
The room is a kitchen
예
Cooling load
18,400 BTU/h
Cooling load
1.53 tons
Next common unit size
24,000 BTU/h
Energy Star chart for this area
16,200 BTU/h

검증 출처: Python decimal: 400 × 20 × 1.25 × 1.2 × 1.1 + 2 × 600 + 4,000 = 18,400; Energy Star 10,000 × 1.1 + 1,200 + 4,000 = 16,200

Shaded 20 m² bedroom, 2.4 m ceiling, good insulation, 1 person

방 면적
20 m²
Ceiling height
2.4 m
Insulation
Good
Sun exposure
Heavily shaded
People who regularly use the room
1
Cooling load
3,433 BTU/h
Next common unit size
5,000 BTU/h
Energy Star chart for this area
5,400 BTU/h

검증 출처: Python decimal: 215.28 ft² × 20 × (7.874/8) × 0.9 × 0.9 = 3,432.6 BTU/h; one occupant adds nothing; chart 6,000 × 0.9

Edge: 150 ft² sits on a chart boundary

방 면적
150 ft²
Ceiling height
8 ft
Insulation
평균
Sun exposure
Normal
People who regularly use the room
2
Cooling load
3,000 BTU/h
Energy Star chart for this area
6,000 BTU/h

검증 출처: Energy Star chart: 150 ft² falls in the “150 up to 250” row (6,000 BTU/h); rule of thumb 150 × 20 = 3,000

자주 묻는 질문

What size air conditioner do I need for my room?

Energy Star's chart for 8 ft ceilings lists 5,000 BTU/h for 100–150 ft², 6,000 for 150–250 ft², 8,000 for 300–350 ft², 10,000 for 400–450 ft², 12,000 for 450–550 ft² and 18,000 for 700–1,000 ft². The 20 BTU/h per ft² rule gives less for small rooms, 6,000 against 8,000 at 300 ft², so the chart figure is shown beside the result.

How many BTU per square foot do I need?

This calculator uses 20 BTU/h per square foot for an 8 ft ceiling. Energy Star's chart works out higher for small and mid-sized rooms: 8,000 BTU/h for 300 ft² is about 27 per ft², and 12,000 BTU/h for 450 ft² is also about 27. At 1,000 ft² the chart's 21,000 BTU/h is 21 per ft², close to the rule.

How many BTU is a ton of air conditioning?

One ton of refrigeration is 12,000 BTU/h, which NIST SP 811 lists as 3,516.853 W; one BTU/h is 0.2930711 W. A 6,000 BTU/h room unit is therefore half a ton or 1.76 kW of cooling, and a 24,000 BTU/h split system is 2 tons or 7.03 kW.

Is a bigger air conditioner better?

No. Energy Star says an oversized unit costs more to buy, wastes energy and does not cool better: it cools the room before it has time to remove the humidity, leaving the air damp and clammy. Choose the unit size that matches the load rather than rounding up by a full size or more for safety.

How do ceiling height and sunlight change the BTU needed?

Energy Star's chart assumes 8 ft ceilings, and this calculator scales the load in proportion to height, so a 10 ft ceiling adds 25%. Energy Star advises 10% less capacity for a heavily shaded room and 10% more for a very sunny one, plus 600 BTU/h for each regular occupant beyond two and 4,000 BTU/h in a kitchen.

“Air conditioner BTU calculator”의 정확도는 어느 정도인가요?

정확도는 입력값과 계산 방법의 가정에 따라 달라집니다. 십진 연산은 유효숫자 50자리를 사용하지만, 추정값·수치해석 방법·원본 데이터의 정밀도는 더 낮을 수 있습니다. 표시값을 반올림해도 이러한 한계는 사라지지 않습니다. 독립적인 출처의 풀이와 대조한 계산 예시: 4. 예를 들어 “300 ft² room, 8 ft ceiling, average everything”은 Python decimal: 300 × 20 = 6,000 BTU/h ÷ 12,000 = 0.5 ton × 0.29307 = 1.758 kW; Energy Star chart row 300–350 ft² = 8,000와 대조해 확인합니다.

이 계산 방법의 출처는 무엇인가요?

ENERGY STAR — Room air conditioners: sizing chart and adjustments; ACCA Manual J 8th Edition (ANSI/ACCA 2 Manual J – 2016) — residential load calculation; NIST SP 811 Appendix B.9 — ton of refrigeration and BTU/h to watt.

이 계산기 소개

Q=20 A h8 fins fsun+600max⁡(0,p−2)+4000 [kitchen]Q = 20\,A\,\frac{h}{8}\,f_{\text{ins}}\,f_{\text{sun}} + 600\max(0, p - 2) + 4000\,[\text{kitchen}]

출처

  1. ENERGY STAR — Room air conditioners: sizing chart and adjustments
  2. ACCA Manual J 8th Edition (ANSI/ACCA 2 Manual J – 2016) — residential load calculation
  3. NIST SP 811 Appendix B.9 — ton of refrigeration and BTU/h to watt

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이 계산기에는 독립적인 출처에서 답을 얻은 계산 예제가 4개 있습니다. 테스트 모음에서 실행되며 여기에서도 실행할 수 있습니다.

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