Colfontaine has 20,811 inhabitants across 13.7 km². The average age is 39, and 69% of residents own their home. Average net income per person is €13,206 a year; households have an average of 1 car, compared with 1.3 nationally. The population is 89.4% Belgian, 6.5% Italian, 1.6% French, 0.4% Algerian, 0.4% Moroccan, 0.2% Cameroonian, 0.2% Spanish and 1.2% other nationalities. Women make up 51.7% of residents.
Houses account for 95.2% of the building stock, while apartment buildings make up 4.8%. Buildings date on average from around 1920. The stock includes 54.9% closed-type houses, 26.9% semi-closed houses, 10% open-type houses, farms and castles, 4.6% buildings and flat blocks, 2.4% commercial houses and 1.1% other types. There are 49 houses for sale in Colfontaine. The listed prices range from €70,000 to €699,999, with an average of €205,408. The average number of rooms is about 5.5, below the national average of 6.
From the centre, access to the A7/E19–E42 towards Halle, Nivelles, Mons and Valenciennes is 8 minutes away; the A15/E42 towards La Louvière, Charleroi, Namur and Liège is reachable in 21 minutes. TEC bus services include lines 1 between Mons and Saint-Ghislain, 11/ and 11 between Saint-Ghislain, Boussu and Hornu, 2 between Mons and Dour, and 4 between Wasmes and Baudour. No metro or tram service is listed. Nearby stations are Frameries, Genly, Saint-Ghislain, Quaregnon and Boussu.
Families have 19 nurseries, 15 nursery schools, 15 primary schools and 2 secondary schools in the municipality. Named examples include Les P'Tits Loups, Ecole Fondamentale Libre De Wasmes-Notre-Dame, Centre Scolaire Saint-Michel De Paturages, Lycee Provincial Hornu Colfontaine and Academie Provinciale Des Metiers. Shops include 1 SPAR, 1 Carrefour and 1 Delhaize. No shared bicycles, shared cars or known EV charging stations are listed. Brussels South Charleroi Airport is 34 minutes away by car or 123 minutes by public transport.