The jetting speed of an inkjet droplet from an inkjet head has been measured, and is widely used in industry to improve jetting performance. The measured jetting speed is used to control the inkjet head by modifying the driving waveform voltage. In jetting speed measurements, the travel distances of an inkjet droplet during two pre-defined timings are used. However, the jetting speed varies significantly during drop formation. If there is a ligament or satellite, the jetting speed is significantly affected. Thus, measured jetting speed using the current methods can differ according to the selection of the two timings. We proposed an instantaneous jetting speed curve to overcome the shortcomings of previous techniques. By determining the instantaneous jetting speed curve, we can understand jetting speed variation during drop formation. Also, the relative jetting speed of satellites with respect to the main droplet during drop formation can be using the proposed approach.