I believe you would like to add scale bar in the layout.
Arcmap > Insert menu > Scale Bar
Hope this is helpful
Kishor
Thanks for response. The process mentioned by you it's applicable for linear scale. Instead I want area scale, which can represent area.
I don't believe there is an area scale feature within ArcMap. If I had to do it I would probably create a custom feature class (polygon) and digitize the area (size) which you wish to represent. For instance three or four adjacent squares of varying size, 1 square foot, 5 square foot, 10 square foot or acres, square mile, whichever you are interested in displaying. Then you can add that polygon to ArcMap document as a New Data Frame. Add the New Data Frame to your Layout which has the existing map, place it somewhere in your title block, and most importantly ensure the scale is identical to your actual map. Then add your text to represent the area sizes. Long process but it would work. Hope this helps, and good luck
Thanks a lot....
Hi Subhas, can you mark this question as answered? Thanks so much.