How is he number of each states electoral votes determined?

Each state has electoral votes equal to the total of the 2 representative the state has in the U.S. Senate plus the number of representative the state has in the House of Representatives. Since every state has two senators and at least one representative to the House, every state has at least 3 electoral votes. The number of representative in the U.S. House of Representatives is fixed at 435. Every 10 years the U.S. Census Bureau takes a census of the population in each state. The 435 representatives in the U.S. House of Representatives is then reapportioned among the 50 states based on the population in each state. The District of Columbia gets 3 electoral votes. Therefore, the total number of electoral votes is fixed at 538 - 100 (senators) + 435 (representatives) + 3 (for DC). The number of electoral votes for individual states may increase or decrease based on the results of the census results.