Abstract The International Reference Ionosphere (IRI) has, for many years now, proven to be a valuable resource for modelling the average ionosphere. Through a series of workshops, improvements and additions have been added, further extending the value obtained from the IRI. Currently, ionospheric variability is receiving attention. Variability is a key characteristic of the ionosphere, which varies over a wide range of time scales, from hours to years. An estimate of ionospheric variability would be a useful addition to the IRI. Recommendations of the International Telecommunications Union [ITU-R HF Propagation Prediction Method Recommendation, International Telecommunications Union, Geneva, 1997, p. 533] offer a tabulation of peak electron density variability used in making HF predictions. This tabulation enables the deciles for peak electron density variability to be calculated using a set of factors, called the decile factors that multiply the median peak electron density, one of the parameters calculated in the IRI. By adapting these factors, it is possible to use them with the IRI. This paper will explore the use of the ITU decile factors adapted for use in the IRI to offer an estimate of ionospheric variability as well as explore their limitations.