Convert kW of IT load to tons and BTU/hr
Every watt delivered to IT equipment leaves the room as heat. There is no envelope gain, no solar load, no occupancy term — the arithmetic that makes conventional HVAC sizing complicated does not apply. Your cooling load is your IT load, converted into whatever unit your mechanical contractor wants to see.
One kilowatt produces 3,412.142 BTU/hr, and one ton of refrigeration removes 12,000 BTU/hr. So a kilowatt of IT load needs roughly 0.284 tons of cooling. A 100 kW room needs about 28.4 tons.
Enter your load below and the calculator returns tons, BTU/hr, and the cooling technology that density actually requires.
Measured or expected draw of the IT equipment, not nameplate.
Every watt delivered to IT equipment leaves as heat, so cooling load equals IT load. One kW is 3,412 BTU/hr; one ton removes 12,000 BTU/hr. This does not include the cooling equipment’s own draw — that shows up in PUE.
Need the full picture — power, cooling, UPS, and circuits together? The full calculator does all of it at once.
Why your cooling load is just your IT load
If you have ever sat through an HVAC sizing exercise for an office, you will remember the load calculation being a long list — heat coming through the walls and roof, sun through the windows, fresh air being brought in, the people in the room, the lights. Add it all up, apply some judgment, get a number.
A data hall throws almost all of that away. No windows to speak of, nobody in there most of the time, and an equipment load so much larger than everything else that the other terms vanish into rounding. So the rule is simply: whatever electrical load you put in, that same amount of heat comes back out. A 100 kW room is a 100 kW heat problem.
This surprises people coming from building services, because it feels too easy. It is genuinely that direct. The one thing it does not include is the power your cooling equipment itself draws — that shows up separately, in PUE.
BTU, BTU/hr, and why the difference matters
A BTU is a quantity of heat — specifically, enough to warm one pound of water by one degree Fahrenheit. A BTU per hour is a rate: how fast heat is moving. Equipment is rated in the rate, not the quantity.
It matters because mixing them up produces answers that are wrong by a factor of however many hours you had in mind. If a spec sheet just says BTU with no time unit, it almost certainly means BTU/hr — but it is worth confirming rather than assuming, especially on anything you are buying.
Some scale for the numbers: a single 500 W server rejects 1,706 BTU/hr. A 5 kW rack rejects 17,061. A row of 42 racks at 8 kW each rejects 1,146,478 BTU/hr. Once you pass a single cabinet the figures get unwieldy, which is exactly why the industry talks in tons or kW instead.
What a "ton" of cooling actually is
The unit is a leftover from the ice trade. One ton of refrigeration is the cooling you would get from melting one ton of ice over 24 hours, which got standardized at 12,000 BTU/hr. It has nothing to do with the weight of the equipment, which trips up almost everyone the first time.
It persists because North American chiller and CRAC capacities are still quoted that way, so if you are talking to a mechanical contractor in the US, tons is the language. Outside North America the same quantity is normally expressed in kW thermal, where the conversion is refreshingly simple — 100 kW of IT load is 100 kW of heat. Flip the calculator to metric and it will show you that instead.
CRAC, if you have not run into it, is a computer room air conditioner: a self-contained unit with its own refrigerant circuit. A CRAH is the chilled-water cousin, fed from a central plant. Both get rated in tons.
The total tells you less than the density
Two rooms, both 500 kW. The first spreads it across 100 cabinets at 5 kW each. The second packs it into 4 cabinets at 125 kW each. Identical tonnage, and the mechanical designs have nothing in common.
The first is a comfortable room you could cool with perimeter units and reasonable airflow discipline. The second cannot be air-cooled at all, at any airflow, and needs liquid running to the chips.
The rough thresholds worth carrying in your head: ASHRAE — the body that publishes the thermal guidelines everyone designs to — treats anything above 20 kW per rack as high density. Air with good containment runs out somewhere around 15 to 20 kW. Rear-door heat exchangers, which bolt a cooling coil onto the back of the cabinet, buy you up to roughly 40 or 50. Past about 50 kW there is no air-based answer left.
Common questions
- How many tons of cooling per kW?
- About 0.284 tons per kW. One kW produces 3,412 BTU/hr and one ton removes 12,000 BTU/hr, so divide your kW load by 3.517 to get tons.
- Do I size cooling to IT load or to facility power?
- To IT load. Facility power includes the cooling equipment itself, so sizing cooling against it would be circular. Use facility power for utility and generator sizing instead.
- Should I add a safety factor to the tonnage?
- Redundancy is the more useful lever. Rather than inflating the load, size to the real load and add N+1 capacity so a unit can fail or be serviced without losing the room.
- What is the exact kW to BTU/hr conversion?
- Multiply kW by 3,412.142. The factor derives from the definitions of the joule and the BTU, so it is exact rather than an approximation.
- How do I convert BTU/hr back to kW?
- Divide by 3,412.142. A 60,000 BTU/hr unit is a 17.6 kW unit.
- Is server heat output the same as its power draw?
- Yes, for practical purposes. Essentially all electrical energy entering a server leaves as heat, so a 500 W measured draw is a 500 W heat load.