Ionogram scaling is the process of reconstructing electron density with respect to height by using the measurements of a remote sensing instrument known as ionosonde. In this study, a novel two-stage ionogram scaling technique, ionogram scaling and electron density (ISED), is proposed. In the first stage, hidden Markov models (HMMs) are used to identify the actual ionospheric reflections in the ionosonde measurements. In the second stage, an International Reference Ionosphere extended to plasmasphere (IRI-Plas) model-based optimization problem is solved to obtain the vertical profile that generates the best least-squares fit to the reflections identified in the first stage. To show the performance of ISED in a global scale, experiments are conducted on 14812 ionograms recorded at the three different stations that are Pruhonice in Czech Republic, Eielson in USA, and Sao Luis in Brazil. Application of ISED to raw ionograms indicates 97.6% of the cases, and ISED provides accurate electron density reconstructions, which is an improvement about 8.7% over automatic real-time ionogram scaler with true height (ARTIST), most commonly used ionogram scaling technique.