The T-casual card costs €12.15 for 10 rides versus €2.40 per single ticket, creating a break-even point at exactly 5.06 trips. After your sixth ride, every subsequent journey saves €2.40. For most 4-day visits involving airport transfer plus daily movement, you'll save €8-12 compared to individual tickets.

Coverage and sharing rules: Valid on metro, buses, trams, and FGC trains within Zone 1, which covers everything from Barcelona airport to Park Güell, Sagrada Familia, and all central neighborhoods. Multiple people can share one card—simply validate once per person each trip.

Where to purchase: Available at any metro station machine (English language option available) or tobacco shops throughout the city. The physical card itself is free and reusable for future Barcelona visits—just reload with more trips when needed.

Practical calculation: If you're traveling from airport (€5.15 on Renfe) plus visiting 3-4 attractions daily requiring metro transport, single tickets quickly cost €15-20 per day. The T-casual reduces this to €6-8 daily, making the mathematics quite clear. For families, one card eliminates constant ticket machine battles while children travel free.