Hello Ritwik,
On ArcPad's Browse toolbar there's the "Measure" tool.
See the ArcPad documentation on "The Browser toolbar":
help.arcgis.com/en/arcpad/10.0/help/index.html#/The_Browse_toolbar/00s100000045000000/
Here's a video of the "Measure" tool in action.
In this video, we measure the width and height of a parcel, then, we measure the permiter of a park.
Stephen