What was the approximate number of British servicemen killed on the first day of the battle of the Somme?

On the first day of the Battle of the Somme, which began on July 1, 1916, approximately 57,000 British servicemen were killed, wounded, or missing. Of these, around 19,240 soldiers were killed, making it one of the bloodiest days in British military history. The massive casualties highlighted the devastating impact of World War I trench warfare.