This is a reverse-chronological list of oil spills that have occurred throughout the world and spill(s) that are currently ongoing. Quantities are measured in tonnes of crude oil with one tonne roughly equal to 308 US gallons, 256 Imperial gallons, 7.33 barrels, or 1165 litres. This calculation uses a median value of 0.858 for the specific gravity of light crude oil; actual values can range from 0.816 to 0.893, so the amounts shown below are inexact. They are also estimates, because the actual volume of an oil spill is difficult to measure exactly.