Similar to the Richter scale used to measure earthquakes, SenderBase's magnitude is a measure of message volume calculated using a log scale with a base of 10. The maximum theoretical value of the scale is set to 10, which equates to 100% of the world's email message volume. Using our log scale, a one point increase in magnitude equates to a 10x increase in actual volume.

For example, with a world wide daily volume of 200 billion messages/day a domain with a magnitude of 5 would have an estimated volume of 2,000,000/day while a sender with a magnitude of 6 would have an estimated daily volume of 20,000,000/day.

The following table illustrates the percentage of Internet email associated with each magnitude: