Estimate rack watts, amp draw, circuit headroom, BTU per hour, cooling tons, monthly kWh, and energy cost for a small server rack, homelab, network closet, or office equipment stack.
Watts to BTU/hr
Amps and circuit headroom
Monthly kWh estimate
Estimate-only planning
Rack result
Estimated load and heat
Estimated rack power0 W
Enter equipment details to estimate rack power.
Total IT load
0 W
Total kW
0 kW
Estimated amp draw
0 A
Full circuit capacity
0 W
Planning target capacity
0 W
Planning headroom
0 W
Target utilization
0%
Heat output
0 BTU/hr
Cooling equivalent
0 tons
Monthly energy
0 kWh
Monthly energy cost
$0
Largest load group
None
BTU/hr uses watts x 3.412142. Cooling tons use BTU/hr divided by 12,000.
How the rack power calculator works
The calculator adds each device group's estimated wattage, then converts that load into kilowatts, amp draw, BTU per hour, cooling tons, monthly kilowatt-hours, and estimated energy cost. The formula for each device group is quantity multiplied by watts each multiplied by average load percentage.
For heat output, nearly all electrical power used by servers, switches, storage, and UPS equipment eventually becomes heat in the room. A practical estimate is watts multiplied by 3.412142 to get BTU per hour.
Why circuit headroom matters
A breaker rating is not the same thing as a comfortable continuous planning load. Many facilities planners use a target such as 80% of circuit capacity for equipment that runs continuously, then leave room for startup surges, power supply losses, future devices, and measurement error.
This page shows both full circuit capacity and the selected continuous-load target. If the estimate is close to or above that target, treat it as a signal to measure actual power draw and get qualified electrical guidance.
What to use for device wattage
The best input is measured power from a UPS, rack PDU, smart plug, or other meter. The next best option is an equipment label or vendor power estimate. Power supply wattage alone can overstate actual draw because it often describes maximum output capacity, not normal running load.
If you are planning a new rack, start conservative. Servers with spinning disks, GPUs, PoE switches, and storage arrays can draw far more power than small routers or lab mini PCs.
Rack power FAQ
Does this include cooling power? The monthly energy estimate covers the rack load you entered. The BTU/hr result estimates the heat the room must remove. Actual HVAC energy depends on the cooling system, room conditions, and facility design.
Can I use this for a data center design? Use it for rough planning and sanity checks only. Data center design needs measured loads, redundancy requirements, power distribution design, cooling design, and local electrical review.
