iPhone · iPad
The HVAC calculator
in your pocket
HVAC Calculator: BTU & AC Load sizes air conditioning and exhaust fans from room dimensions — offline, in 20 languages, with the projects you measured kept between visits. Free to use.
What it does
Cooling load
Room dimensions in feet or metres give capacity in BTU/h, tons, kilowatts and horsepower at once, with a toggle for sun-exposed rooms.
Exhaust fan airflow
Sixteen room presets with their recommended air-change rates — bathrooms, kitchens, laundries, workshops — returning CFM and m³/h.
Works offline
Everything is calculated on the device. No signal in a plant room or a basement makes no difference.
Saved projects
Keep the rooms you measured on a walkthrough instead of re-entering them; dimensions are stored in metres so switching units never loses precision.
20 languages
English, Spanish, Portuguese, French, German, Italian, Arabic, Hindi, Bengali, Indonesian, Turkish, Vietnamese, Thai, Japanese, Korean, Chinese, Polish, Dutch and Persian.
Same numbers as this site
The calculators here run the app's formulas, so a figure you quote from the web matches the one on your phone.
App or website?
| Tool | iOS app | This site |
|---|---|---|
| Cooling load / BTU | Yes | Yes |
| Exhaust fan CFM | Yes | Yes |
| Duct sizing (ductulator) | — | Yes |
| Room-by-room load | — | Yes |
| Unit converters | In every result | Dedicated pages |
| Saved projects | Yes | — |
| Works offline | Yes | — |
The app is the field tool; the site carries the wider set of calculators and the reference charts. Both use the same formulas.
FAQ
- Is the HVAC Calculator app free?
- Yes — the calculators are free to use. An optional one-time Pro purchase lifts the limit on saved projects; nothing is behind a subscription.
- What does the app calculate?
- Two things: air conditioning cooling load from room dimensions, and exhaust fan airflow from room type and volume. Duct sizing, load breakdowns and the unit converters live on this website rather than in the app.
- Does it work without internet?
- Yes. Every calculation runs on the device, so the app works in basements, plant rooms and anywhere else without signal.
- Is there an Android version?
- No. The app is iOS only, for iPhone and iPad. On Android, the calculators on this site work in any mobile browser.
- Which iOS version does it need?
- iOS 17 or later. The download is small — under 10 MB.