Municipality Trzin, which is part of the Osrednjeslovenska statistical region, measures 9 km2; this ranks it 210th among Slovene municipalities.

Statistical data for 2013 reveal the following:

In the middle of 2013 about 3,900 people (about 1,900 men and 2,000 women) were living in the municipality, which ranks Trzin 131st among Slovene municipalities. The population density was 451 people per square kilometre, which was higher than the national average of 102 people per square kilometre.

The number of live births was higher than the number of deaths, which means that natural increase per 1,000 population in the municipality was positive. It was 2.8 (in Slovenia 0.9). The number of people who moved from the municipality was higher than the number of people who moved into the municipality, so net migration per 1,000 population in the municipality was negative. It was -8.8. The sum of natural increase and net migration per 1,000 population in the municipality was negative. It was -5.9 (in Slovenia 1.1).

The mean age of people in Trzin was 40.9 years, which was lower than the national average (42.2).

In contrast to most Slovene municipalities, in Trzin the number of young people was higher than the number of old people: there were 98 people, aged 65 or more, per 100 people aged 0–14. This ratio shows that the value of the ageing index was lower than the national average of 119. It also shows that the mean age of people in Trzin is growing more slowly than in Slovenia as a whole. Data by sex show that the ageing index for women was in all Slovene municipalities higher than the ageing index for men. In Trzin – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was exactly the opposite.

Trzin had 2 kindergarten. They were attended by 255 children or 83% of all children aged 1–5, which was more than the national average of 75%. In the school year 2013/2014 basic school in Trzin was attended by about 390 pupils, while various upper secondary schools were attended by about 150 pupils. There were 50 students and 11 graduates per 1,000 people in the municipality; in Slovenia the averages were 44 per 1,000 and 9 per 1,000, respectively.

Among people aged 15–64 (i.e. working age population) about 62% were persons in employment (i.e. persons in paid employment or self-employed persons), which is more than the national average of 57%.

The registered unemployment rate was 8.7%, which is less than the national average (13.1%). In contrast to most Slovene municipalities, more men than women were unemployed.

In Trzin, average monthly gross earnings per person employed by legal persons were about 2% lower than the annual average of monthly earnings for Slovenia; and net earnings about 2% lower.

In 2013, there were 379 dwellings per 1,000 population. About 78% of dwellings had at least three rooms. Average size of dwellings in the municipality was 93 m2.

About every person in Trzin had a car (70 passenger cars per 100 population); cars in this municipality were on average 7 years old.

In 2013, 497 kg of municipal waste per person was collected in Trzin, which is 177 kg more than on average in Slovenia.