AC Tonnage Calculator
Estimate AC tonnage from room area, sun exposure, and occupancy (planning estimate).
Last reviewed by the Radiatus Cloud team
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Work out the AC size a room needs
An air conditioner must match the room, and undersizing or oversizing both cause problems. This calculator estimates the AC tonnage from room area, sun exposure and occupancy for planning.
Why matching tonnage to the room matters
AC capacity is measured in tons, and the right size depends on how much heat the room gains, from its area, how much sun it gets, and how many people are in it. An undersized unit runs constantly and never cools; an oversized one cools too fast, cycles off, and leaves the room humid and uncomfortable. Estimating the tonnage from the room’s characteristics gives a planning figure to choose a unit that actually suits the space, which is far better than the common rule-of-thumb guess that ignores sun and occupancy.
A planning estimate
These are estimates from a standard method for general planning, not professional advice; confirm anything important for your specific situation. It runs entirely in your browser, so nothing you enter is uploaded and it works without an account, keeping your data on your own machine.
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Frequently Asked Questions
How is AC tonnage estimated?
From the room area, its sun exposure, and how many people occupy it, since all three affect the heat the AC must remove.
What happens if the AC is undersized?
It runs constantly and struggles to cool the room, using more energy while never reaching a comfortable temperature.
What happens if it is oversized?
It cools too fast and cycles off before removing humidity, leaving the room cold but clammy and uncomfortable, and wearing the unit.
Why include sun and occupancy?
Because a sunny room or a crowded one gains more heat, needing more capacity than area alone suggests, which rule-of-thumb estimates miss.
Is my data uploaded?
No. The calculation runs entirely in your browser.
Privacy & Security
Calculated locally in your browser. Use as a rough estimate.
How to Use
Enter room area and conditions to estimate required AC tonnage.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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