Pension insurance is a social security program. Fundamental principles of pension insurance are the principles of mutuality and the principles of solidarity, which in their application are complemented by the principles of independence and inalienability of rights and legitimacy. The pension insurance system is based on generational solidarity and the Croatian Pension Insurance Institute is responsible for its implementation. Pension legislation is applied to it, including the Pension Insurance Act, the Pension Insurance Act, the Pension Insurance Act and other related bylaws. The system is based on three pillars of insurance, of which the first two are mandatory, and contributions are paid by the employer, and the third pillar represents a voluntary pension insurance. The first pillar is called a pillar of generational solidarity, while the second pillar represents individual capitalized savings as well as the third pillar of pension insurance that is voluntary. The system works in such a way that members of the system and their employers pay their salaries and wages during their lifetime. This graduation thesis deals with retirement as a concept, calculations and types of retirement, as well as on the calculation of income from self-employment and salaries calculation. Before the examples calculation of pensions with some income, pension calculation is analyzed when it is higher than average net wages and pension calculation when it is lower than the average net wage. Within calculation of pensions at work, several different situations have been analyzed – the calculation of pensioner's income when pensioner works only half of the working time, pensioner's income accrual by the contract on the work and the calculation of the royalty for the work of a pensioner.