Tons = BTU/hr ÷ 12,000. 12,000 BTU = 1 ton, 18,000 BTU = 1.5 tons, 24,000 BTU = 2 tons. Type in either box; it converts both ways.
MBH = BTU/hr ÷ 1,000. Equipment spec sheets and commercial drawings often list capacity in MBH.
Capacity in all units, the kind of equipment sold at that size in the US, and the floor area it typically cools in a moderate US climate (Zone 3). Areas use the same model as the AC size chart: single rooms up to 18,000 BTU, whole homes above that.
| BTU/hr | Tons | kW (thermal) | Watts (thermal) | US equipment | Cools (US, moderate) | India, per room |
|---|---|---|---|---|---|---|
| 5,000 | 0.42 | 1.47 | 1,465 | Window or portable unit | ~230 sq ft | — |
| 6,000 | 0.5 | 1.76 | 1,758 | Window or portable unit | ~270 sq ft | — |
| 8,000 | 0.67 | 2.34 | 2,345 | Window or portable unit | ~360 sq ft | — |
| 9,000 | 0.75 | 2.64 | 2,638 | Window unit or mini-split | ~410 sq ft | 100–130 sq ft room |
| 10,000 | 0.83 | 2.93 | 2,931 | Window unit or mini-split | ~450 sq ft | 110–150 sq ft room |
| 12,000 | 1 | 3.52 | 3,517 | Window unit or mini-split | ~550 sq ft | 130–180 sq ft room |
| 14,000 | 1.17 | 4.10 | 4,103 | Window unit or mini-split | ~640 sq ft | 150–210 sq ft room |
| 15,000 | 1.25 | 4.40 | 4,396 | Window unit or mini-split | ~680 sq ft | 160–220 sq ft room |
| 18,000 | 1.5 | 5.28 | 5,276 | Mini-split, or the smallest central system | ~820 sq ft | 200–270 sq ft room |
| 24,000 | 2 | 7.03 | 7,034 | Central system (2 ton) | up to ~1,170 sq ft (whole home) | 260–360 sq ft room |
| 30,000 | 2.5 | 8.79 | 8,792 | Central system (2.5 ton) | up to ~1,530 sq ft (whole home) | 330–450 sq ft room |
| 36,000 | 3 | 10.55 | 10,551 | Central system (3 ton) | up to ~1,890 sq ft (whole home) | — |
| 42,000 | 3.5 | 12.31 | 12,310 | Central system (3.5 ton) | up to ~2,260 sq ft (whole home) | — |
| 48,000 | 4 | 14.07 | 14,068 | Central system (4 ton) | up to ~2,630 sq ft (whole home) | — |
| 60,000 | 5 | 17.59 | 17,585 | Central system (5 ton) | up to ~3,390 sq ft (whole home) | — |
kW and watts here are cooling output, not electricity use. For power draw see tons to kW & electrical draw. Hot climates (Zone 1) cover about 20% less area than shown; cool climates (Zone 5) about 20% more.
1 MBH = 1,000 BTU per hour. The M is the Roman numeral for a thousand, so a 36 MBH unit is 36,000 BTU/hr, or 3 tons. The same quantity is written kBtu/h in DOE and ENERGY STAR documents. Do not confuse MBH with MMBH (or MMBtu/h), which means a million BTU per hour and is used for large boilers.
| BTU/hr | MBH | Tons |
|---|---|---|
| 12,000 | 12 MBH | 1 |
| 18,000 | 18 MBH | 1.5 |
| 24,000 | 24 MBH | 2 |
| 30,000 | 30 MBH | 2.5 |
| 36,000 | 36 MBH | 3 |
| 42,000 | 42 MBH | 3.5 |
| 48,000 | 48 MBH | 4 |
| 60,000 | 60 MBH | 5 |
| 90,000 | 90 MBH | 7.5 |
| 120,000 | 120 MBH | 10 |
| 180,000 | 180 MBH | 15 |
| 240,000 | 240 MBH | 20 |
Residential split systems stop at 60 MBH (5 tons); the larger rows are light-commercial and rooftop sizes.
AC capacity is written three ways depending on who is talking: US equipment and Manual J reports use BTU/hr, Indian and most international markets sell by tons, and engineering documents and European spec sheets quote thermal kilowatts. Spec sheets for the same unit frequently mix all three, which is why a 1.5-ton split, an 18,000 BTU window unit and a 5.3 kW cassette are the same amount of cooling. Keep thermal output separate from electrical draw: a unit's cooling kW is 3–5× its power consumption, with the ratio set by its SEER2 or ISEER rating — the bill calculator handles that side.
Divide BTU per hour by 12,000. One refrigeration ton is 12,000 BTU/hr, so 24,000 BTU is 2 tons and 9,000 BTU is 0.75 ton.
Exactly 1 ton (3.52 kW of cooling). In a moderate US climate that cools about 550 sq ft of a single room.
18,000 BTU/hr, or 5.28 kW of cooling. Multiply tons by 12,000 to get BTU.
3 tons. As a US central system it covers up to about 1,890 sq ft of whole-home area in a moderate climate.
Yes. AC capacity labelled "BTU" always means BTU per hour. A 10,000 BTU window unit removes 10,000 BTU of heat every hour.
MBH means a thousand BTU per hour. 1 MBH = 1,000 BTU/hr, so a 60 MBH furnace or AC is 60,000 BTU/hr (5 tons of cooling). DOE and ENERGY STAR write the same unit as kBtu/h.
3 tons. Multiply MBH by 1,000 to get BTU/hr (36,000), then divide by 12,000. As a shortcut, tons = MBH ÷ 12.
BTU ↔ tons chart · Tons ↔ kW, HP & electrical draw · Amps & breaker size · Room size by tonnage
Or skip the conversion and size the room directly with the AC tonnage calculator or BTU calculator.