AC Tonnage Calculator
Cooling tonnage for a room from area, occupancy, glazing and equipment — better than sq-ft rules.
1 TR = 3.517 kW = 12,000 BTU/h. The lazy 100 sq-ft/ton rule ignores sun and people — west glass alone can add half a ton.
Formula
Note: Screening estimate for warm climates; use full Manual J / heat-load software for ducted systems.
AC Tonnage Calculator is a free ac tonnage calculator for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About AC Tonnage Calculator
Cooling tonnage for a room from area, occupancy, glazing and equipment — better than sq-ft rules. The calculation implements Q = 65·A + 25·A(roof) + 115·persons + 220·A_glass + equipment (ACCA Manual J (simplified residential loads); ISHRAE residential guidance). 1 TR = 3.517 kW = 12,000 BTU/h. The lazy 100 sq-ft/ton rule ignores sun and people — west glass alone can add half a ton.
How to use AC Tonnage Calculator
- 1Enter Floor area in m².
- 2Enter Occupants.
- 3Enter Window area (sun-exposed) in m².
- 4Enter Equipment + lighting in W.
- 5Read Cooling load, Tonnage instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use AC Tonnage Calculator?
- ✓Implements the standard formula — Q = 65·A + 25·A(roof) + 115·persons + 220·A_glass + equipment
- ✓Reference cited on-page: ACCA Manual J (simplified residential loads); ISHRAE residential guidance
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Built-in engineering verdict flags out-of-range results instantly
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the AC Tonnage Calculator use?+
It computes Q = 65·A + 25·A(roof) + 115·persons + 220·A_glass + equipment, per ACCA Manual J (simplified residential loads); ISHRAE residential guidance. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
1 TR = 3.517 kW = 12,000 BTU/h. The lazy 100 sq-ft/ton rule ignores sun and people — west glass alone can add half a ton. Note: Screening estimate for warm climates; use full Manual J / heat-load software for ducted systems.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the AC Tonnage Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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