Transformer sizing calculator — kVA
Turn connected load into a transformer rating: enter load kW and power factor, add load factor and future growth, and read the kVA to order.
Transformer kVA from connected load
Formula: kVA = kW / PF — required rating applies the load factor, future growth and safety margin; the recommended size is the next standard 3-phase rating. Full-load amps: I (A) = kVA × 1000 / (√3 × V).
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Frequently asked questions
How do I size a three-phase transformer?
Start from connected load in kW, divide by power factor to get kVA, apply the load factor and add a future-growth margin (typical 20%) plus safety margin (10%). Round up to the next standard size (15, 30, 45, 75, 112.5, 150, 225, 300, 500 …).
What is the difference between kW and kVA?
kW is real (working) power; kVA is apparent power. They relate by the power factor: kVA = kW / PF. A transformer is rated in kVA because it must supply both the working power and the reactive power the load needs.
What transformer rating do I need for a given load?
For a 60 kW load at 0.85 PF the load kVA is about 71. With 20% growth and 10% margin that becomes ~94 kVA → select the next standard size, 112.5 kVA. This calculator does the whole chain.
AO Ctrl provides this tool for reference only.