The vega value of a derivative instrument, a spread, or a position multiplied by the notional principal. It corresponds to the sensitivity in dollar to a 1% move in the implied volatility of an underlying asset. In options, this tool measures in monetary terms the impact of change of an option price with respect to volatility. If an option value (OV) with volatility moving up one unit and the same value with volatility moving down one unit are denoted, respectively, as OV(+1), OV(-1), then:

Dollar vega= OV(+1) – OV (-1)

It is also known as a position vega.