A crude oil price barrel chart shows the price per barrel of oil on the vertical axis and the progression of time on the horizontal axis. The level of the price line on the vertical axis gives the price per barrel at the time on the horizontal axis.
It is important to understand the amount of time a chart of oil prices per barrel represents when interpreting such a chart. Some charts reflect long spans of time of months or years, while other charts show continuous activity over a day or even an hour. Prices reflected on an oil price chart over a long term typically use the closing price of oil to represent the price of oil on a particular day, though some charts may show average prices over days, weeks or months as well. Large fluctuations on a chart with a short time frame often indicate market volatility, while changes on longer term charts represent systemic shifts in oil prices due to world events.
Oil charts also often show prices in inflation-adjusted constant monetary units rather than actual prices at the historical time of the chart. If this is the case, it is necessary to reverse the adjustment for inflation to arrive at the actual price of oil per barrel at the time.