What can I do in Paris on a small budget?

Paris Musées runs the municipal museum network, and admission to the permanent collections is free of charge for all visitors at twelve of its museums. The two exceptions are the Paris Catacombs and the Archaeological Crypt of the Île de la Cité, which remain ticketed. The network has fourteen City of Paris museums in all, and they open Tuesday to Sunday from 10:00 a.m. to 6:00 p.m., with hours occasionally extended for late openings. Temporary exhibitions inside them are ticketed separately — the free rule applies to the standing collections.

Set that against the cost of the national institutions and the saving is substantial. The Louvre charges €32 for non-EEA visitors and €22 for visitors from the European Economic Area for its standard admission. For an American traveler, two Louvre tickets cost more than a week of municipal museums costs for a family.

The weather is the third lever, because so much of what is free in Paris is outdoors. Paris-Montsouris averages 177.3 hours of sunshine in April and 203.5 in June — the second-highest monthly figure of the year — against an April precipitation normal of 1.80 inches (45.8 mm). April in particular is a strong budget month: more than five and a half hours of sun a day on average, moderate rainfall, and rates below the summer peak.

The quays below street level along the Seine are the cheapest good hours in the city. They sit a flight of steps down from the traffic, out of the noise, with the stone warm underfoot by mid-afternoon in spring and the bridges arriving one after another as you walk. Nothing about it costs anything.

The free municipal collections are not minor holdings. The network includes houses and studios of individual artists and writers as well as large civic collections, and because admission is free there is no sunk cost in staying twenty minutes — which changes how you use them. The practical trick is the Monday-Tuesday inversion: the City of Paris museums close on Mondays while the Louvre stays open, and the Louvre closes on Tuesdays while the municipal network is open. A week planned around that alternation never has a dead day and never needs a second expensive ticket.

• Tuesday to Sunday, 10:00 to 18:00 — The free municipal collections. Pick two in the same district and walk between them.
• Any day, any hour — The Seine quays and bridges of the World Heritage property. No ticket, no closing time.
• April or June — The best sunshine-to-rainfall ratio for a trip spent largely outdoors, at 177.3 and 203.5 monthly sunshine hours.

The free admission applies to permanent collections only, and the headline temporary exhibitions in the same buildings are charged — it is easy to arrive for a publicized show and find it is the part that costs money. The Catacombs and the Archaeological Crypt are excluded from the scheme entirely. On the national side, the €32 non-EEA Louvre rate is per person and applies regardless of how long you stay, so a budget trip is better served by one long late-opening visit than by two short ones. And the municipal Monday closure removes the free option for a full day each week, which needs planning for rather than discovering.

The Paris things-to-do answer in this group explains the Louvre's late-opening evenings in detail, and the Paris food answer covers the counter-and-market approach that keeps eating costs down.