Where does ForeFlight get its Magnetic Variation numbers?

Magnetic Variation information comes from multiple sources, including the FAA, NavCanada, Jeppesen, etc. If the data we receive is old or not available for specific locations, then we perform internal calculations to determine magnetic variation.

For VOR's, the original declination is used (Variation of the VOR at the last or only adjustment).

We do a dynamic calculation of Magnetic Variation as a route is planned. The result is Magnetic Variation values that are current based on a model for the current date.