This rack heat load calculator converts the electrical load of your servers, storage and network equipment into heat, because practically every watt a server draws ends up as heat the cooling has to remove. It runs entirely in your browser: nothing you type is sent to our server.
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Table of Contents
The conversions
- 1 W of electrical load = 1 W of heat = 3.412 BTU/h.
- 12,000 BTU/h = 1 ton of refrigeration (about 3.517 kW).
- From current: watts = amps × volts × power factor (0.95-0.99 for servers with modern power supplies).
Use real power, not the PSU rating
A server with two 800 W power supplies rarely draws more than 300-400 W. Use measured figures from the PDU, the BMC (ipmitool dcmi power reading) or the vendor’s power calculator. Nameplate ratings lead to oversized, inefficient cooling.
Rack density
Up to about 8 kW per rack can usually be cooled by room air with good airflow management. 8-15 kW needs hot or cold aisle containment, and above 15 kW in-row or liquid cooling is normal. For the airflow those racks need, see the airflow (CFM) calculator.
How we checked it
We checked the sample rack on 11-12 October 2026: 6,560 W of devices = 6.56 kW, 22,384 BTU/h and 1.87 tons; 10 A at 230 V with a power factor of 0.95 = 2.19 kW.
Frequently asked questions
How many BTU does a server produce?
Multiply its power draw in watts by 3.412. A server drawing 350 W produces about 1,194 BTU/h.
How do I convert kW to tons of cooling?
Multiply kW by 3,412 to get BTU/h and divide by 12,000. 5 kW is about 1.42 tons.
Should I use the power supply rating?
No. Use measured power. Power supply ratings are maximums and are usually two to three times the real draw.