How many colonists remained loyal to Britain during the war for independence?
According to the Calhoon (2005, see the source below), about 15–20% of the 2 million white colonists were Loyalists, people who remained loyal to Great Britain and who were opposed to the American Revolution (as opposed to Patriots, who supported the Revolution). This means that about 300,000–400,000 people were Loyalists at the outset of the American Revolution. (Some sources quote the number of Loyalists at 500,000 people.)
Following the Revolution, most loyalists remained in the United States and became citizens. However, about 60,000 people left (see Jasanoff in the sources below). The majority of those who left went to Canada, including New Brunswick, Quebec, Nova Scotia, and Prince Edward Island. Others went to Florida or to England. Those who had slaves brought them with them.
Calhoon, Robert M. "Loyalism and neutrality", p. 235; Middlekauff (2005) pp. 563–564; Thomas B. Allen, Tories: Fighting for the King in America's First Civil War (2010).
Jasanoff, Maya. (2012). Liberty's Exiles: American Loyalists in the Revolutionary World. Random House. p. 357.