How is transformer oil quantity calculated for different transformer ratings?

Oil quantity is not derived directly from kVA alone. It is determined by transformer design: tank volume, radiator volume, conservator volume, and required expansion space for temperature rise. Practical calculation uses manufacturer data, drawings, or nameplate information, and utilities often maintain capacity tables by transformer model and cooling class. For approximate planning, higher kVA units generally have more oil because they dissipate more heat and require larger tanks and cooling surfaces, but two transformers with the same rating can have very different oil volumes.