Single and 3 Phase Transformer kVA Calculator and kVA Formula
In power systems, determining the correct transformer kVA (kilovolt-amperes) is crucial for efficient energy distribution and safety. Both single phase and 3 phase transformers require precise kVA calculations to ensure they can handle electrical loads without risk of overheating or failure. This page provides the kVA formula for both single phase and 3 phase transformers and includes a calculator to help you quickly and accurately determine the required transformer capacity.
KVA calculations for transformers are vital to determine the transformer's capacity, ensuring it can handle the electrical load efficiently and safely. By calculating KVA, one can size transformers appropriately, maintain stable voltage levels, optimize energy efficiency, and meet compliance standards, all of which are essential for the reliable and cost-effective operation of electrical systems.
Transformer KVA formula
The formula to calculate the apparent power (in kVA) for both single-phase and three-phase transformers is based on the rated voltage and rated current.

As mentioned the formula for single-phase transformers is straightforward, while the formula for three-phase transformers takes into account the square root of 3 (approximately 1.732) due to the phase difference between the currents in a three-phase system. In the formula, KVA is apparent power in kilovolt-ampere (KVA), "V" is the rated voltage of the transformer and "I" is the rated current of the transformer.
Single Phase Transformer KVA Calculator
Example of Single Phase transformer KVA calculation :
Voltage = 11000 volt , current = 5.75 Amp
Single phase transformer KVA = 63.25 KVA
3 Phase Transformer KVA Calculator
Example of 3 phase transformer kva calculation :
Voltage = 11000 volt , current = 5.75 Amp
Single phase transformer KVA = 109.55 KVA
Conclusion
Whether you’re working with a single phase or 3 phase transformer, accurate kVA calculations are essential for
reliable and efficient power systems. By using the single phase and 3 phase transformer kVA formulas and our calculator,
you can select the correct transformer size to meet load requirements, ensuring longevity and stability in electrical applications.
➨Also refer Transformer basics and types.
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