Although the famine itself probably resulted in about 1 million deaths, the resultant emigration caused the population to drop by a further 3 million. About 1 million of these are estimated to have emigrated in the immediate famine period, with the depression that followed continuing the decline until the second half of the 20th century. These migrants largely ended up in North America, with some in Australia and in Britain.

Most people paid their own fares to make the trip, although perhaps 3% had their fares paid by their Landlords. The cheapest fares were to Canada, around 55 shillings, while a fare to the USA cost between 70 shillings and £5 (100 shillings). There were two ways one could travel; either in a standard class or steerage. Standard passengers had berths and could walk on the deck. Steerage passengers were crowded together below decks and often could not use the deck. For many emigrants, steerage was the most they could afford.

Between 1845 and 1855, 1.5 million people left for good. In 1845, emigration was at the pre-famine rate of 50,000 per year. In 1846 100,000 left. It peaked in 1847, when 250,000 left. Over the next 5 years it averaged 200,000 per year, before the numbers fell off. By 1855, the rate was down to 70,000 per year