How can I find the charge under a portion of the curve on a CV plot?
This FAQ applies to versions 1.2.3208 and greater.


An “area tool” can be placed on the CV plot to find the area under a selected portion of the curve. However, this tool calculates the results purely mathematically, giving power (in watts). What an electrochemist wants to know is the total charge for that area.

Find the charge under a portion of the curve on a CV plot

There are two choices:

The first is to instead place the area tool on the current-versus-time (I-vs-T) plot so that the result is already a charge. The difficulty with this is knowing where to place the limits of the area tool (since the CV plot does not provide time data). An advantage of this method is that the results may be more accurate since any noise in the measured potential of the CV data can adversely affect the area calculation, whereas the corresponding X-axis on the I-vs-T is time, which will have neither noise nor measureable jitter.

The second is to manually divide the results of the area tool (power, i.e. Volts x Amps) by the sweep rate of the CV (Volts/sec, known from the experiment parameters) to find the charge (Amps x secs). If this result needs to be displayed on the plot, right-click and empty area of the plot and select “Add text” to display that calculated value.