Travelmath provides an online travel time calculator to help you figure out flight and driving times. You can compare the results to see the effect on the total duration of your trip. Usually, the flight time will be shorter, but if the destination is close, the driving time can still be reasonable.
Another popular tool is the time difference calculator, which can be used to check the time zone change anywhere in the world. This is especially useful if you're making international calls, since you can find the best time to schedule your phone call.