ADR - Average Daily Rate

Average Daily Rate (know as ADR) stands for the average revenue per occupied room for a certain time period. 
The ADR can calculated by dividing the room revenue by the number of rooms sold.

Total room revenue for a period / number of rooms sold = ADR

Together with other measurements like the Occupancy rate, RevPAR and BAR a hotel can do analysis on how well the hotel is performing over a certain period. Furthermore it can be used to compare performance with other similar hotels