Workers at BJP's headquarters in New Delhi passed around traditional Indian sweets and chanted tributes to leader Narendra Modi who, polls show, is likely to emerge as prime minister.
Vote counting started at 2.30am GMT (10am AEST) on Friday after a six-week parliamentary election that saw a record 551 million people hit the polls.
"People have voted for development and progress. People are restless for change. They will feel liberated once results are announced," BJP spokesman Mukhtar Abbas Naqvi told reporters.
Election Commission officials have banned victory processions in India's holiest Hindu city of Varanasi, where Modi is standing, and throughout the electorally critical northern state of Uttar Pradesh.
The state's chief election official, Umesh Sinha, told AFP the decision was "aimed at maintaining law and order in the state".
Violence in Uttar Pradesh's Muzaffarnagar district last September between Muslims and Hindus left some 50 people dead and forced thousands to flee their homes.
The ruling Congress party, expected to face a defeat after 10 years in power, has warned that a BJP victory will stoke interreligious tensions in the Hindu-majority country.
Violence flared in the southern city of Hyderabad on Wednesday in which three people were killed during clashes between Muslims and Sikhs.
The BJP's previous best showing was in elections in 1998 and 1999 when it won 182 seats and ran the country until a shock defeat in 2004.
Exit polls, which failed to predict the 2004 reversal, forecast that the right-wing National Democratic Alliance (NDA) led by the BJP should garner a majority of 272 seats - with other allies keen to join.
