A method and apparatus for controlling the volume of ink droplets ejected from thermal ink jet printheads is disclosed. The electrical signals applied to heating elements for generating droplet ejecting bubbles thereon are composed of packets of electrical pulses. Each pulse and spacing therebetween are varied in accordance with one or more whole, clock or timing units. The number of pulses per packet and width of pulses and spacing therebetween are controlled in accordance with the manufacturing tolerance variations, the location of the addressed heating element in the printhead, the number of parallel heating elements concurrently energized, and optionally the temperature of the printhead in the vicinity of the heating elements to maintain the desired volume of the ejected droplets.