Watts to BTU Calculator

Convert the power IT equipment draws into the heat it gives off, in BTU per hour and tons of cooling.

Inputs

Result

Enter the power in watts to see the heat in BTU/hr and tons.

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How the calculation works

Heat output follows directly from the electrical power drawn:

BTU/hr = watts × 3.41214
tons of cooling = BTU/hr ÷ 12,000

One watt is 3.412142 BTU/hr (International Table BTU, per NIST Special Publication 811). The calculator uses 3.41214; most references round to 3.412, which changes results by less than 0.01%. One ton of refrigeration is defined as 12,000 BTU/hr.

The calculator assumes all the electrical power the equipment draws becomes heat in the room, which holds for servers, storage and network gear. For a realistic heat load, enter measured or typical draw rather than power supply ratings, which are maximums.

This converts one figure. Sizing cooling for a whole room also adds lighting, people, heat through walls and windows, and a design margin, and the cooling equipment’s own capacity depends on the conditions it runs in.

Worked example

A colocation cabinet draws 10,000 W (10 kW):

BTU/hr = 10,000 × 3.41214 = 34,121 BTU/hr
tons = 34,121 ÷ 12,000 = 2.84 tons

With the rounded factor 3.412 the heat output is 34,120 BTU/hr, 1.4 BTU/hr less.

A single 500 W server:

BTU/hr = 500 × 3.41214 = 1,706 BTU/hr
tons = 1,706 ÷ 12,000 = 0.142 tons

Frequently Asked Questions

How many BTU/hr does a 10 kW rack give off?

About 34,121 BTU/hr, or 2.84 tons of cooling, assuming all 10,000 W the rack draws ends up as heat in the room.

Does all the power a server draws turn into heat?

For cooling purposes, yes. Practically all the electrical energy IT equipment uses ends up as heat in the room; what leaves as network signals or as light from status LEDs is negligible. That is why cooling for IT spaces is sized from the electrical load.

Is it BTU or BTU per hour?

Heat load and cooling capacity are rates, so the unit is BTU per hour (BTU/hr or BTU/h). An air-conditioner label that says 12,000 BTU means 12,000 BTU/hr. A BTU on its own is an amount of energy, about 1,055 joules.

Should I use 3.412 or 3.41214?

Either. One watt is 3.412142 BTU/hr using the International Table BTU (NIST SP 811), usually rounded to 3.412. The difference is under 0.01%: 1.4 BTU/hr on a 10 kW load.