@Dhiraj
the maximum % of HRA is defined in income tax act, and geographical map of urban, semi urban, rural is available with local CA, who can guide better, in connection with specific percentile as per the residence pin code of employee
normally the employers does not touch the maximum ceiling limit, as over 1 lacs rent per annum needs rent agreements and rental payment receipts to assess the TDS applicable, and in absence of proper documentation whole the HRA are subjected for TDS