Shift margins in down and cross track directions and skew angle were investigated using micromagnetic simulation with a shielded planar head for patterned media with an areal density of 1 Tbit/in2. The shift margins were quantitatively estimated using parameters of the head field and the magnetic properties of media. It is essential to use a head with a higher field gradient and a medium with a small field width between saturation and nucleation fields, to obtain a larger down track shift margin, and a head with a narrower cross track field distribution to obtain a larger cross track shift margin and skew angle margin.