🏢 Commercial Cooling Tonnage, RTU Staging & CFM
Size commercial HVAC for offices, retail, restaurants, server rooms and warehouses. Get the required cooling tonnage, a recommended rooftop unit (RTU) staging combination, and the fresh-air ventilation CFM — factoring business type, occupancy, internal heat loads, ceilings and climate.
🏢1. Building Type
Each building type carries a different internal heat load — a restaurant kitchen or server room runs far hotter than an office or warehouse.
📐2. Floor Area & Ceiling
Range: 500 – 50,000 sq ft
👥3. Occupancy & Internal Loads
Auto-set from building type & area — adjust to your peak headcount.
🌍4. Climate & Unit Staging
Multiple staged RTUs give redundancy (if one fails, the building stays partly cooled) and better part-load efficiency — the commercial standard.
Commercial AC Tonnage by Building Type & Size
Commercial cooling isn't one-size-fits-all — a restaurant needs 3–4× the tonnage of a warehouse of the same size because of kitchen, lighting and occupancy heat. This chart shows typical cooling loads; use the calculator above for your exact staging and CFM.
| Building Type | Rule of Thumb | Typical Load (per 1,000 sq ft) |
|---|---|---|
| Office / Professional | 1 ton per ~350 sq ft | ~2.8 Tons |
| Retail Store | 1 ton per ~250 sq ft | ~4.0 Tons |
| Restaurant / Kitchen | 1 ton per ~150 sq ft | ~6.5 Tons |
| Server / IT Room | 1 ton per ~150 sq ft | ~6.5 Tons |
| Warehouse / Industrial | 1 ton per ~600 sq ft | ~1.7 Tons |
These are planning rules of thumb for packaged rooftop units (RTUs) at standard ceilings. High ceilings, hot climates, heavy glazing, dense occupancy and process equipment push tonnage up — the calculator factors all of it.
How Commercial RTU Sizing Works
Commercial load estimation follows ACCA Manual N and ASHRAE guidance. The calculator combines four load sources, then adds a safety and ventilation layer.
1. Building Envelope Load
Floor area × a per-square-foot factor for the building type × a ceiling-height multiplier. Taller ceilings mean more air volume to cool, so a 20 ft warehouse carries a higher factor than an 8 ft office.
2. Occupancy & Equipment (Internal Gains)
Each person adds about 400 BTU/hr of body heat, which matters enormously in dense spaces like restaurants and retail. Lighting and equipment add another layer — a commercial kitchen or gym generates several times the heat of an office.
3. Sun, Glazing & Climate
Large storefront glass and hot Sun-Belt or humid-South climates raise the load with multipliers. An internal server room with no windows in a northern climate sits at the low end; a west-facing restaurant in Phoenix sits at the top.
4. RTU Staging & Ventilation
Commercial buildings rarely use one giant unit. The calculator splits the load into multiple standard RTUs (3, 4, 5, 6, 7.5, 10 ton…) so that if one fails the building stays partly cooled, and part-load efficiency improves. It also computes the fresh-air CFM your ventilation must supply (ASHRAE 62.1) and the total supply airflow at ~400 CFM/ton.
Frequently Asked Questions
How many tons of commercial AC do I need per square foot?
Why do commercial buildings use multiple RTUs instead of one large unit?
What size RTU do I need for a 2,000 sq ft restaurant?
How is commercial fresh-air ventilation (CFM) calculated?
What's the difference between an RTU and a split system?
Do I still need an engineer if I use this calculator?
Related tools from Refcon HVAC
- AC Tonnage Calculator (residential)
- Ductless Mini-Split Calculator
- AC Electricity Cost Calculator
- BTU Load Calculator
Last updated: 2026. Reviewed by the Refcon HVAC engineering team using ACCA Manual N & ASHRAE 62.1 guidance. Planning estimate — confirm with a licensed commercial mechanical engineer. Tell us about an error.
Estimates vary by contractor. Compare free quotes from licensed local pros before you commit. Request a quote →
High-efficiency systems may qualify for utility rebates and federal or state incentives. Find current programs at ENERGY STAR & DSIRE.
Figures are reviewed by the Refcon HVAC engineering team using U.S. DOE, ENERGY STAR & ACCA Manual J data. Estimates only — confirm with a licensed pro.