Abdi Adem Arabica coffee, constant factor, leaf area, linear model 141-146 4 (3) 2020 July, 2020 The present study was conducted with the objective to develop linear model for coffee leaf area measurement. Leaves were collected from 47 coffee cultivars that were field planted at Mechara Agricultural Research Center, West Harerge Zone, in July 2005 and are currently under evaluation. For leaf sample collection, four plants were randomly selected for each of the 47 cultivars from eastern Ethiopia. Five normal leaves were detached from each sample plant and used for data collection. Variation among constant factor (K) of the coffee cultivars was determined using R² value in both linear and logarithmic regression. The result of the study revealed that leaf area parameters were highly and positive correlation (from 0.90 to 0.95 at P< 0.01). K value for leaf area measurement varied from 0.45 to 0.89 and with mean value of 0.68. The R² values of 47 constant factor (K) of the 47 coffee cultivars was 0.002 in linear regression and 0.0008 in logarithmic regression and was negligible. Hence, mean value of 0.68 can be used as K along with leaf length and leaf width for coffee leaf area determination. LA= 0.68*LL*LW (where LA is leaf area, LL- leaf length and LW- leaf width) is recommended for coffee leaf area measurement. The information generated through this investigation may be useful for the coffee breeders to develop suitable coffee varieties and in deciding breeding strategy for the coffee breeding programme.