Municipality Mirna Peč, which is part of the Jugovzhodna Slovenija statistical region, measures 48 km2; this ranks it 137th among Slovene municipalities.
Statistical data for 2015 reveal the following:
In the middle of 2015 about 2,900 people (about 1,500 men and 1,400 women) were living in the municipality, which ranks Mirna Peč 159th among Slovene municipalities. The population density was 60 people per square kilometre, which was lower 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 6.6 (in Slovenia 0.4). The number of people who moved from the municipality was lower than the number of people who moved into the municipality, so net migration per 1,000 population in the municipality was positive. It was 6.6. The sum of natural increase and net migration per 1,000 population in the municipality was positive. It was 13.1 (in Slovenia 0.6).
The mean age of people in Mirna Peč was 39.9 years, which was lower than the national average (42.6).
in contrast to most Slovene municipalities, in Mirna Peč the number of young people was higher than the number of old people: there were 78 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 123. It also shows that the mean age of people in Mokronog – Trebelno 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 Mirna Peč – in contrast to most Slovene municipalities – fewer women were 65+ years old than 14 or less; for men the situation was exactly the opposite.
In the school year 2015/2016 basic school in Mirna Peč was attended by about 250 pupils, while various upper secondary schools were attended by about 150 pupils. There were 50 students and 12 graduates per 1,000 people in the municipality; in Slovenia the averages were 39 per 1,000 and 9 per 1,000, respectively.
Among people aged 15–64 (i.e. working age population) about 65% were persons in employment (i.e. persons in paid employment or self–employed persons), which is more than the national average (58%).
The registered unemployment rate was 7.2%, which is less than the national average (12.3%). As in most Slovene municipalities, more women than men were unemployed.
In Mirna Peč, average monthly gross earnings per person employed by legal persons were about 16% lower than the annual average of monthly earnings for Slovenia; and net earnings about 12% lower.
In 2015, there were 388 dwellings per 1,000 population. About 65% of dwellings had at least three rooms. Average size of dwellings in the municipality was 85 m2.
Every other person in Mirna Peč had a car (56 passenger cars per 100 population); cars in this municipality were on average 9.4 years old.
In 2015, 216 kg of municipal waste per person was collected in Mirna Peč, which is 99 kg less than on average in Slovenia.