What size level should I buy first?

Across the reviewers we read, the common advice in r/Tools and r/Carpentry is to own both a compact torpedo (around 8 to 12 inches) for tight spots, conduit and hanging tasks, plus a 48-inch box or I-beam level for doors, cabinets and siding. A 48-inch span catches errors a short level misses, while a torpedo fits in a pocket. Many shoppers start with a torpedo and add a 4-foot level as projects grow.