The Human Development Index (HDI) is an index used by the United Nations and various nongovernmental organisations (NGOs) to categorise and rank countries by their level of development. HDI scores can help prioritise a country's needs, as well as assist in helping organisations target problem areas such as education and longevity. Learn how to calculate an HDI score to get a more holistic picture of a country's overall development needs.

Understand the three major areas of development that the Human Development Index focuses on: health, education and income. Health focuses on longevity and the life expectancy of a country's residents at birth. Education measures adult literacy, as well as the percentage of residents enrolled in various levels of education. Finally, income measures the gross domestic product (GDP) of a country in U.S. dollars. Together, these factors show varying levels of development that can pinpoint specific areas that need work. For example, a country may seem developed to outside critics if it has a high GDP, but an HDI score may reveal that its health levels are low.

Learn how countries are ranked in terms of their HDI scores. A score of "1" is a perfect score, meaning a country is as developed as possible. A score of "0" is given to a country with no level of development. Countries are ranked between the two extremes by decimal point to the thousandths place. Most countries in the West rank in the 70th to 80th percentile, marking a relatively high level of development.

Calculate the health score in the Human Development Index. Visit the United Nations Statistics Division (link in the Resources section) and obtain the life expectancy at birth for the country in which you are interested. Subtract 25 (the lowest acceptable age of life expectancy, according to the UN) from this number. Divide the final amount by "85 -25." Write down the resulting quotient.

Calculate the education score in the Human Development Index. Visit the UN Data page for gross enrolment ratio in tertiary and secondary education (link in the Resources section). Click the country you are interested in and obtain the gross enrolment number. Subtract "0" from this, then divide the total by "100." Write down the quotient.

Obtain the literacy rate for your country from the UN Statistics Division (link in the Resources section). Divide the literacy rate by "100" and write down the quotient.

Add 2/3 of the quotient in Step 4 with 2/3 of the quotient in Step 5. The resulting sum is the Human Development Index score for education.

Calculate the Gross Domestic Product (GDP) score for your Human Development Index. Obtain the GDP number for your country from the UN Statistics Division (link in the Resources section).

Input the GDP into the following equation, replacing "GDP" with the number listed in the statistics data: log(GDP) - log(100). Write down the total. Divide by log(40,000) - log(100). Write down the quotient.

Calculate the total Human Development Index number for the country you've chosen by combining the data from the previous steps. The HDI is calculated by adding 1/3 of the quotient in Step 3, 1/3 of the quotient in Step 6, and 1/3 of the quotient in Step 8. The sum is the country's Human Development Index.