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BTU to Tons

42,000 BTU to Tons

42,000 BTU per hour equals 3.5 refrigeration tons. That's a 3.5 ton AC size.

Find it on the AC's label or spec sheet.

Cooling capacity

Your 42,000 BTU AC is a 3.5 ton AC.

3.5tons

Sold as a 3.5 ton AC. Exact: 3.5 tons.

1 ton = the cooling of melting 2,000 lb of ice per day.
Cooling kW
12.309

1 refrigeration ton = 12,000 BTU/hr. Cooling kW is cooling capacity, not electricity use.

  • Tons = BTU/hr ÷ 12,000
  • Cooling kW = BTU/hr × 0.2930710702 ÷ 1,000
Your numbers42,000 ÷ 12,000 = 3.5
Decimal places

Common AC ratings

Choose a capacity to fill the calculator, or open its worked example.

Worked examples:6,0009,00012,00018,00024,00036,000

How the conversion works

Divide 42,000 by 12,000 to convert the capacity.

42,000 ÷ 12,000 = 3.5 tons

Cooling capacity: 12.309 cooling kW. Cooling kW is not the electricity the AC uses.

Compare 42,000 with 36,000 and 48,000 BTU/hr

Compare 42,000 with 36,000 and 48,000 BTU/hr
BTU/hrTonsCooling kWSize class
36,000310.55063 ton
42,0003.512.3093.5 ton
48,000414.06744 ton

Does 3.5 tons mean it fits my space?

A refrigeration ton is a capacity unit, equal to 12,000 BTU/hr; it is not the unit's weight.

There is no universal area-to-tonnage ratio. Room conditions, building design and climate affect the required capacity.

Whole-home systems require a separate load calculation.