How do you work out va for a transformer?

To calculate the volt-amperes (VA) for a transformer, you multiply the primary voltage (V) by the primary current (A) or the secondary voltage (V) by the secondary current (A), depending on which side of the transformer you are analyzing. This gives you the apparent power in volt-amperes (VA). Typically, the formula is VA = V × I, where V is the voltage and I is the current for either the primary or secondary side, ensuring that you account for the correct phase angle if applicable.