14 free calculators · nothing leaves your browser
Infrastructure maths,
without the spreadsheet
Power, cooling, rack space, fibre and capacity calculators for data center and network engineers. Unit-tested formulas, worked examples, no signup.
Browse by category
Each category page explains the constraint it covers and where the usual mistakes are.
Power
3Rack PDU capacity, UPS runtime and PUE — the three numbers that decide how much equipment a cabinet can actually carry.
- PDU Load Calculator
- UPS Runtime Calculator
- PUE Calculator
Cooling
2Convert electrical load to heat load, size cooling capacity, and check whether air can actually reach the rack that needs it.
- Cooling Load Calculator
- Airflow (CFM) Calculator
Space & Weight
3Rack unit planning, raised floor loading and cable tray fill — the physical limits that decide what fits.
- Rack Unit (U) Planner
- Floor Loading Calculator
- Cable Tray Fill Calculator
Network
4IPv4 subnetting, optical loss budgets, transfer times and structured cabling labels.
- Subnet Calculator
- Fiber Loss Budget Calculator
- Data Transfer Time Calculator
- +1 more
Cost & Capacity
2Compare colocation pricing models on like-for-like terms, and project when you run out of headroom.
- Colocation Cost Calculator
- Capacity Growth Planner
Start here
The four people reach for most often.
- PDU Load CalculatorPowerCalculate usable rack PDU capacity in kW from voltage, breaker rating and phase, with the 80% continuous-load derate and N+1 redundancy applied.
- Cooling Load CalculatorCoolingConvert IT load in kW to BTU/hr and tons of refrigeration, and size CRAC/CRAH capacity including a redundancy margin.
- Rack Unit (U) PlannerSpace & WeightPlan rack elevations by U height: total used, free U remaining, and percentage utilisation with a reserved-space allowance.
- Subnet CalculatorNetworkCalculate network address, broadcast, usable host range, wildcard mask and host count from any IPv4 address and CIDR prefix.
The numbers are tested
Every formula is a pure function with unit tests against known values — 1 kW is 3412 BTU/hr, a 208 V 30 A three-phase PDU derates to 8.65 kW. Wrong numbers on an engineering tool are worse than no tool.
Nothing is uploaded
Everything runs as static JavaScript in your browser. There is no backend to send data to and no account to create. Open your network tab and check.
The context is included
Each page explains the formula, works an example, and says plainly what the calculation does not cover — because that is usually where the expensive surprises live.