AC Tonnage Calculator
AC Tonnage Calculator — quick estimate
Estimate the cooling load (in TR) your space needs from a quick heat-load model. Adjust the inputs for an instant figure — then get a proper engineered HVAC design from our team.
Your space
Quick estimate from a sensible+latent heat-load model. Server rooms assume IT heat load; a detailed survey (glazing, orientation, equipment) is needed for the final design.
Cooling load is the estimated demand; recommended capacity is the nearest practical installed selection.
Get an engineered HVAC design — free
Our mechanical engineers will run a full heat-load and recommend the right VRF / ductable / chiller system for your space. We'll attach the estimate above automatically.
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Indicative pre-sales estimate only — not a binding design. Final tonnage and unit selection depend on glazing, orientation, insulation, ventilation, internal equipment heat and operating hours, and must be confirmed by a detailed heat-load survey.
How this calculator works — and where it stops
What it calculates
A cooling-load estimate in TR and kW for a conditioned space, the recommended installed capacity, a suggested unit configuration and the fresh-air quantity.
Inputs
- Space type — office, retail, glass-fronted space, conference, restaurant, server room or residential
- Floor area
- Number of occupants
- Climate — hot-dry, hot-humid or moderate
- Fresh-air requirement
Method
- Envelope and internal load: floor area × a base load per square foot for the space type (from 60 BTU/hr per sq ft for residential to 200 for server rooms) × a climate factor (1.10 hot-dry, 1.12 hot-humid, 1.00 moderate).
- Occupant load: 255 BTU/hr sensible and 205 BTU/hr latent per person, with the latent part adjusted for climate (0.85 to 1.30) and for activity by space type.
- The sum is multiplied by a diversity factor for the space type, converted to TR at 12,000 BTU/hr, and the recommended capacity carries a 1.07 design factor. Unit configuration is chosen from standard sizes to minimise oversizing, with a small penalty per additional unit.
Assumptions
- The base loads are typical values for Indian commercial interiors with ordinary glazing and lighting; they stand in for a room-by-room heat-load calculation.
- Fresh air is added as a quantity, not as a coil load — the latent load of outdoor air in a humid climate is only approximated through the climate factor.
- Occupancy is at design peak.
Limitations
- No glazing orientation, wall or roof U-values, shading, lighting watts or equipment schedule — the inputs a real heat-load calculation is built on.
- Process loads, cleanroom requirements, 24×7 operation and precision-cooling tolerances are not modelled.
- The result is a demand estimate, not a system selection; chilled water, VRF and split systems suit different load profiles at the same TR.
Worked example
Produced by running this calculator with the inputs below.
Inputs
- Space: office
- Area: 5,000 sq ft
- Occupants: 40
- Climate: hot-dry
- Fresh air: ASHRAE occupancy basis
Working
- Envelope and internal: 5,000 × 65 BTU/hr per sq ft × 1.10 (hot-dry) = 357,500 BTU/hr
- Occupant sensible: 40 × 255 = 10,200 BTU/hr
- Occupant latent: 40 × 205 × 0.85 (hot-dry) × 1.0 (office activity) = 6,970 BTU/hr
- Sum × 0.95 diversity = 355,937 BTU/hr ÷ 12,000 = 29.7 TR (104.3 kW)
- Design factor 1.07 → 31.7 TR target; nearest practical configuration without heavy oversizing is 32.0 TR
Result. 29.7 TR calculated load; 32.0 TR recommended installed capacity as 1 × 20 TR + 1 × 12 TR; 169 sq ft per TR; fresh air 850 m³/hr.
How engineers use the result
As a first-pass number for plant-room and electrical-load reservation, and to sanity-check a vendor's proposed capacity against the space before the design basis exists.
When a professional design must replace it
Before equipment is selected: a heat-load calculation on the actual drawings, occupancy and equipment schedule replaces this estimate, and TAB after installation proves it.
Need an exact BOQ, rate analysis or measurement sheet?
This is a quick engineering estimate. For tendering, billing or audit, our QS & estimation team prepares an item-wise BOQ, rate analysis and a verified measurement sheet to IS / CPWD norms — backed by 15+ years and ISO 9001:2015 quality processes.
Got your number — what next?
A calculator gives you a first figure. These take it further.
The work itself
Read before you specify
The terms behind it
Delivered work with this scope
- Electrical & Mechanical for a Global Manufacturer— client withheld
- Bespoke MEP for a Global Semiconductor Leader— NXP Semiconductors