When measuring for a new dishwasher install, there are a few key measurements and installation requirements you need before you buy.
1) Most dishwashers are a standard 24" wide and 24" deep BUT the height (from the floor to under the countertop) can vary especially if new floors have been put in since the old dishwasher was installed. 34" is the magic number. If we have 34" any dishwasher will fit in and any old dishwasher can be removed. If we have <34", please let your salesman know so we can look at other options.
2) All new dishwashers CANNOT drain under the floor they sit on. Water will siphon out and your dishes will never be clean. Usually a drain extension is required to drain under the sink or a plumber is required to install a stand pipe that will fit behind the dishwasher.
3) Any dishwasher that is not located next to a sink can also be problematic. Please let your salesman know if your dishwasher is not next to your sink/sink cabinet so arrangements can be made for your installation.