How many BTU per hour is one watt?

1 W = 3.412142 BTU/hr. A 10 kW rack therefore rejects 34 121 BTU/hr of heat, and every watt drawn by IT equipment becomes heat inside the room.

How many kW is a ton of refrigeration?

A ton of refrigeration is 12 000 BTU/hr, which is 3.5169 kW (3.516851 kW from 12 000 ÷ 3.412142). Cooling units are sold in tons in North America and in kW almost everywhere else.

Why size the CRAC above the calculated load?

The calculated figure is the steady-state heat rejection. A sizing factor covers compressor cycling, part-load efficiency, filter loading, and the fact that you will add equipment. The tool states the factor it applied so you can change it.

Does a UPS or PDU add to the cooling load?

Yes, but far less than the IT load. Losses in the electrical path — typically 2–6 % of throughput — also end up as heat in the room, so add them if the room is close to its limit.

BTU & Cooling Load Calculator

From vendor documentation

A live converter between watts, kilowatts, BTU/hr, tons of refrigeration and kcal/h, plus CRAC sizing: enter the rack load, see the heat rejection and the recommended unit size with a stated redundancy factor.

Live converter

Edit any field; the other four follow.

This is the field driving the conversion.

BTU/hr

ton (refrigeration)

kcal/h

CRAC sizing

A stated factor, not a hidden fudge

Sizing factor

Covers compressor cycling at part load, filter loading, and the equipment you will add later. 1.3 is a common planning figure.

Why a factor at all

The calculated figure is steady-state heat rejection under perfect conditions. Real units cycle, lose capacity as filters load, and are sized from a catalogue of discrete models — so the required capacity is the calculated load multiplied by this factor, and the recommended unit is the next whole ton above that.

Export

Conversion table and CRAC sizing

Cooling load

24.000 kW of IT load rejects the same amount of heat

BTU/hr: 81891.41
Tons of refrigeration: 6.824284
Kilowatts: 24
kcal/h: 20636.28
Watts: 24000
Round-trip drift: exact

CRAC / CRAH sizing

Rack load in: 24 kW
Sizing factor: × 1.3
Required capacity: 8.87 ton
Recommended unit: 9 ton

Worked conversion

Every step the numbers above went through

Chain

24 kW → 24000.000000 W
24000.000000 W × 3.412142 BTU/hr per W = 81891.4080 BTU/hr
81891.4080 BTU/hr ÷ 12000 BTU/hr per ton = 6.824284 ton
6.824284 ton × 3.516852 kW per ton = 24.000000 kW

One ton of refrigeration is 12 000 BTU/hr = 3.5169 kW

The ton is a rate of heat transfer, not a mass: it is the cooling needed to freeze one short ton of ice in 24 hours, which works out at 12 000 BTU/hr. That is 3.5169 kW (3.516851 kW from 12 000 ÷ 3.412142 BTU/hr per watt). North American equipment is sold in tons; almost everywhere else it is sold in kW.

Definitions used

The constants behind every conversion

BTU/hr per watt: 3.412142
BTU/hr per ton: 12,000
Watts per ton: 3516.8525
kW per ton: 3.516852
kcal/h per watt: 0.859845
Conversion basis: BTU/hr

1 ton = 12 000 BTU/hr1 W = 3.412142 BTU/hr1 ton = 3.516851 kW

Frequently asked

How many BTU per hour is one watt?: 1 W = 3.412142 BTU/hr. A 10 kW rack therefore rejects 34 121 BTU/hr of heat, and every watt drawn by IT equipment becomes heat inside the room.
How many kW is a ton of refrigeration?: A ton of refrigeration is 12 000 BTU/hr, which is 3.5169 kW (3.516851 kW from 12 000 ÷ 3.412142). Cooling units are sold in tons in North America and in kW almost everywhere else.
Why size the CRAC above the calculated load?: The calculated figure is the steady-state heat rejection. A sizing factor covers compressor cycling, part-load efficiency, filter loading, and the fact that you will add equipment. The tool states the factor it applied so you can change it.
Does a UPS or PDU add to the cooling load?: Yes, but far less than the IT load. Losses in the electrical path — typically 2–6 % of throughput — also end up as heat in the room, so add them if the room is close to its limit.

Frequently asked

Next