# BTU Calculator for Portable Air Conditioners (Free, 2026)

> Free BTU calculator: enter room size, ceiling height, sun exposure and people — get the right cooling capacity (BTU) plus a matching portable AC model instantly.

Canonical (HTML, zitierfähig): https://getecoback.com/en/guide/btu-calculator.html

Live data on this page (hourly, rendered in the browser, not included in this Markdown view): https://getecoback.com/api/heat

Too few BTU and your room never gets cool; too many is wasted money and needlessly loud. Enter your room details and the calculator gives you the right cooling capacity plus a unit sized to match.

As an Amazon Associate, EcoBack earns from qualifying purchases. The product links in the result are affiliate links — you pay the same price. The calculator is guidance, not a guarantee.

**In short:** as a rule of thumb you need about **340 BTU per m²**. Rough guide: **up to 15 m² → 7,000–9,000 BTU**, **15–25 m² → 9,000–12,000 BTU**, **25–35 m² → 12,000–14,000 BTU**, **over 35 m² → 14,000+ BTU**. Add capacity for high ceilings, strong sun (south/west or top-floor), several people or an open kitchen. The calculator below does this automatically.

Room size (m²)

Ceiling height

Standard (up to 2.6 m)
High (over 2.6 m)

Sun exposure

Low (north, shaded)
Normal
High (south/west, top-floor)

People in the room

Open kitchen / many heat sources in the room
Calculate BTU

## BTU by room size — quick reference

Even without the calculator, these are the common guide values for a portable air conditioner by room size (at normal ceiling height and average sun exposure).

Room size |
Recommended BTU |
Typical room |
Matching model |

up to 15 m² |
**7,000–9,000 BTU** |
small bedroom, office |
Comfee (value) |

15–25 m² |
**9,000–12,000 BTU** |
bedroom, home office |
De'Longhi Pinguino (sweet spot) |

25–35 m² |
**12,000–14,000 BTU** |
living room |
Klarstein (large rooms) |

over 35 m² |
**14,000+ BTU / monobloc** |
open-plan space |
Klarstein (high-BTU) |

Models compiled from public reviews, not tested by us. For high ceilings, south/top-floor rooms or several people, size one step up — the calculator above does this automatically.

## How the BTU calculator works

The base is about **340 BTU per m²**, adjusted for ceiling height, sun exposure, people (each person beyond two adds heat) and heat sources such as an open kitchen. It's a proven rule of thumb — the exact figure also depends on insulation and windows. For the full breakdown see our [guide to how many BTU you need by room size](https://getecoback.com/en/guide/how-many-btu-do-i-need.html).

## Frequently asked questions

**How many BTU do I need for my room?**As a rule of thumb, about 340 BTU per square metre. Rough guide: up to 15 m² needs 7,000–9,000 BTU, 15–25 m² needs 9,000–12,000 BTU, 25–35 m² needs 12,000–14,000 BTU, and over 35 m² needs 14,000+ BTU. Add capacity for high ceilings, strong sun, several people or an open kitchen.

**What happens if the air conditioner has too few BTU?**An underpowered unit runs at full load constantly, never reaches the target temperature and still uses a lot of power. Size to your room or slightly above.

**Is more BTU always better?**No. An oversized unit short-cycles on and off, cools unevenly, is louder and costs more to buy. Matching the room is best.

**Keep reading:**
[Best portable air conditioner for the 2026 heatwave →](https://getecoback.com/en/guide/best-portable-air-conditioner-europe-heatwave.html)
[How many BTU do I need? (full table) →](https://getecoback.com/en/guide/how-many-btu-do-i-need.html)
[Portable AC with tilt-and-turn windows →](https://getecoback.com/en/guide/portable-ac-tilt-and-turn-windows.html)
[🌡️ Heat Check: how hot does your room get? →](https://getecoback.com/en/guide/heat-check.html)

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Maschinenlesbare Übersicht: https://getecoback.com/for-agents.html · Sizing-Datensatz (CC BY 4.0): https://getecoback.com/sizing-data.json
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Note: EcoBack does not test devices itself; picks summarise public tests. The site is funded via Amazon affiliate links on the HTML pages — this Markdown view deliberately contains none.