OBJECTIVES: Idiopathic pulmonary fibrosis (IPF) is a rare and fatal lung disease. EQ-5D utilities, an important consideration for cost-effectiveness analysis, are not commonly reported in IPF clinical trials. On the other hand, the St George’s Respiratory Questionnaire (SGRQ) is the most extensively used patient reported outcome measure in IPF patients. The objective of this study was to develop a mapping algorithm from the total SGRQ score to obtain EQ-5D utilities. METHODS: Data were analysed from a double-blind multicentre study conducted in England and Wales of which 181 IPF patients received either co-trimoxazole or placebo. In total, 202 pairs of data were collected recording both SGRQ and the EQ-5D-3L. Generalised mixed models, accounting for repeated measurements within subjects as residual or generalised random effects, were fit to the data. Explanatory variables were evaluated to aid model fit: Age; BMI; Sex; Forced Expiratory Volume in 1 second (FEV1); Forced Vital Capacity (FVC); and FEV1/FVC. Additionally, the potential non linearity of the relationship between explanatory and response variables was explored by investigating transformations and fitting restricted cubic splines with 4 knot points. Goodness of fit statistics determined the best fitting model. RESULTS: The generalised random effects model was the best fitting model. The addition of explanatory variables, use of transformations and investigation of a restricted cubic spline did not improve model fit. The final mapping algorithm, EQ-5D = 1.3246 – 0.01276*SGRQ, was associated with a root mean squared error of 0.1391. Inspection of the scatter plot showed that EQ-5D utilities predicted by the mapping algorithm closely approximated observed values from the study. CONCLUSIONS: A mapping algorithm was developed to estimate EQ-5D utilities from the total SGRQ score in IPF patients. This may be useful for researchers conducting cost-effectiveness analysis when EQ-5D utilities are not available from IPF clinical trials.