The general section of many pilot operating handbooks (POH), as well as checklists, typically only provide a single speed for lift off. These speeds are often associated with the aircraft's maximum takeoff weight.
An aircraft departing at less than max gross weight may be able to lift off at a speed less than what is published in the general section of the POH. ForeFlight Runway Performance determines lift off speed using performance data from the aircraft and the calculated takeoff weight for the flight.
If the calculated takeoff weight is less than the max gross takeoff weight, a lower lift off speed than what is published in the general section can be expected. Refer to the performance section of your aircraft's POH to verify lift off speeds.
Example lift off speeds by weight