Conventional SAR resolution equations cannot be applied to ultrawideband ultrawidebeam systems, particularly, bistatic ultrawideband ultrawidebeam systems. This is because the dependence of system frequency response in the range and across range is not considered. In this case, area resolution, i.e., area of the resolution cell, will be an alternative. This article introduces a new area resolution formula for bistatic ultrawideband ultrawidebeam SAR systems based on the relationship between radar signal frequency, range, and cross-range wavenumbers for bistatic synthetic aperture radar.