A 1,500 sq ft home in a moderate US climate typically needs a 3-ton (36,000 BTU) air conditioner — but climate, sun exposure, ceilings and insulation can shift that by a full ton. Enter your real room data below to get the exact tonnage, BTU and running cost.
Estimate only — confirm equipment sizing with a Manual J load calculation by a licensed contractor.
| Cooling load | — |
| Thermal power | — |
| Floor area | — |
| Duct airflow needed | — |
Every tool runs entirely in your browser. No accounts, no uploads, no tracking of your inputs.
Paste your AC's model number (Goodman, Carrier, Trane, Voltas, LG…) and we'll decode its tonnage from the capacity code.
→ TOOL · 03Add every room, sum the loads, and get a central-system size or per-room split AC plan — no signup required.
→ TOOL · 04Monthly running cost from tonnage, star rating / SEER2, daily hours and your local tariff.
→ TOOL · 05Instant conversions between BTU/hr, refrigeration tons, kilowatts, kcal/hr and horsepower.
→ TOOL · 06Portable units cool less than the box claims. Size by the DOE's derated SACC rating instead.
→ TOOL · 07Tonnage → watts → amps, with MCB / breaker size guidance for a dedicated circuit.
→ TOOL · 08Per-zone ductless sizing with multi-zone totals, from 9,000 BTU bedrooms to 36,000 BTU open plans.
→ TOOL · 09Right-size a 5,000–24,000 BTU window unit for a single room without overshooting.
→ TOOL · 10Offices, shops and server rooms — heavier occupant and equipment loads handled properly.
→TOOL · 11Airflow (CFM) and round or rectangular duct sizing by system tonnage and duct role.
→Typical central AC size by home area — moderate US climate (Zone 3), average insulation, 8 ft ceilings.
| Area | Cooling load | AC size |
|---|---|---|
| 600 sq ft | 13,200 BTU/hr | 1.5 ton |
| 1,000 sq ft | 22,000 BTU/hr | 2 ton |
| 1,500 sq ft | 33,000 BTU/hr | 3 ton |
| 2,000 sq ft | 44,000 BTU/hr | 4 ton |
| 2,500 sq ft | 55,000 BTU/hr | 5 ton |
| 3,000 sq ft | 66,000 BTU/hr | 5 ton + zone |
Garages, sunrooms, server rooms and classrooms don't follow bedroom math — each page below explains that space's load physics with a calculator pre-tuned for it.
A two-car garage (~440 sq ft) carries loads a same-size bedroom never sees: the envelope is usu…
→SPACEA resting occupant adds ~600 BTU/hr; someone mid-workout puts out 1,000–1,500 BTU/hr, so a home gym needs far more cooling than its size suggests…
→SPACELow internal gains (two sleeping people, no appliances), night-time operation when outdoor temp…
→SPACEA living room's load swings more than any other room: two people watching TV on a Tuesday, ten …
→SPACECooking appliances dump roughly 4,000 BTU/hr of ambient heat into the room while in use — a gas…
→SPACEStandard sizing assumes walls that resist heat; a sunroom's envelope is designed to admit it. S…
→SPACEAn attic room doesn't sit under a roof — it sits inside one. Heat soaks through the sl…
→SPACEBelow-grade walls sit against ~13°C earth — a basement's sensible cooling load is a fraction of…
→SPACEA desktop workstation, two monitors and peripherals dissipate 300–500 W continuously — roughly …
→SPACEElectronics turn nearly all input power into heat, so server rooms are sized on equipment watts (BTU/hr = watts × 3.412), not floor area…
→SPACERetail loads stack three things homes don't: door-opening infiltration every few minutes (a gla…
→SPACEA seated diner adds ~600 BTU/hr; a full 24-cover dining room carries roughly 13,000 BTU/hr of extra load from people, lighting and kitchen heat…
→SPACEA hair dryer is a 1,500–2,000 W heat gun — ~5,000–6,800 BTU/hr while running. With two or three…
→SPACEFifteen people training add 15,000–22,000 BTU/hr of body heat and a torrent of…
→SPACEA classroom is the purest occupancy-driven load: 30 students at ~600 BTU each is about 17,000 BTU/hr before sun and equipment…
→SPACEManufactured homes combine the three worst load multipliers: 2-inch wall cavities (a fraction o…
→SPACEA conservatory is glazing on five of six surfaces — including the roof, the worst one. Summer s…
→SPACEA 90 sq ft study with one occupant and a laptop carries one of the lightest loads in the house …
→Straight answers, sized for both US central systems and Indian split ACs.
In a moderate US climate, 1 ton (12,000 BTU/hr) cools roughly 500–600 sq ft of average-insulated space. In hot Indian conditions the same ton covers only 100–140 sq ft of a single room, because split ACs fight much higher solar and ambient heat loads.
An oversized unit cools the air quickly but shuts off before removing humidity — a behavior called short-cycling. You get a cold, clammy room, more compressor wear, and a higher bill.
It's coded in the outdoor unit's model number, not the serial number. Look for a two-digit group like 18, 24, 30, 36, 42, 48 or 60 — capacity in thousands of BTU; divide by 12 for tons. Our Model Number Decoder does this automatically for 22 brands.
No. This is a Manual J-style estimate using the same load factors (area, climate, ceilings, sun, occupants, windows, insulation). A licensed contractor should run a full Manual J before you buy a central system.
applies ACCA Manual J–style load factors (area, climate zone, ceiling, sun, occupants). For final central-system sizing, a full ANSI/ACCA 2 Manual J is the standard — ACCA. See our full methodology.