A washing machine appliance and methods of operating a washing machine appliance are provided. The washing machine appliance includes a motor and a rotatable basket. The motor is operated to rotate the basket to a first speed. The basket is then decelerated from the first speed to a second speed less than the first speed. A deceleration time is determined while decelerating the basket from the first speed to the second speed. The method may include, or the washing machine appliance may be configured for, determining a size of a load of articles in the basket of the washing machine appliance based on the deceleration time. Based on the determined size of the load, one or more operating parameters of the washing machine appliance are selected and an operation of the washing machine appliance is performed according to the one or more selected operating parameters.