A method of estimating a total amount of soot in a diesel particulate filter includes monitoring a pressure differential across the diesel particulate filter; monitoring an engine speed and an engine load from an engine in fluid communication with the diesel particulate filter; determining a first soot mass estimate from the monitored pressure differential, the first soot mass estimate having an associated confidence indicator based on the monitored engine speed and engine load; determining a second soot mass estimate from the monitored engine speed and engine load; and outputting the first soot mass estimate if the confidence indicator is above a predetermined threshold, and outputting the second soot mass estimate if the confidence indicator is below the predetermined threshold.