How much does transformer oil weigh per litre or gallon?

Transformer mineral oil density is typically around 0.87 to 0.90 kg per litre at room temperature, varying by formulation and temperature. In practical logistics planning, a common rule is roughly 0.88 kg per litre, so a 200 litre drum weighs about 176 kg of oil plus drum mass. For US gallons, multiply litres by 3.785, then apply density. Weight matters for transport limits, crane and forklift selection, bund capacity calculations, and spill response planning. Always use the product data sheet density and correct it for temperature if high accuracy is needed.