Packing for a 4-day vacation in 2026 is all about the "gold-standard" of versatile layers and carry-on efficiency. Start with the "Rule of 3": pack three tops and three bottoms that can all be interchanged to create up to nine outfits. Wear your bulkiest items—like jeans, a jacket, and your heaviest walking shoes—on the plane to save space. For a 4-day trip, you can typically fit everything into an "under-seat" bag or a standard 22-inch carry-on by using compression packing cubes, which organize your clothes and save up to 30% of your bag's volume. Focus on "tech-fabrics" or merino wool that are wrinkle-resistant and can be worn twice. For toiletries, stick to solid versions (shampoo bars, stick sunscreen) to bypass the "3-1-1" liquid rules and prevent leaks. A "pro-tip" for 2026 is to pack a lightweight, foldable daypack inside your main bag for excursions. By being ruthless about "just-in-case" items and sticking to a cohesive color palette, you can navigate your entire long weekend without ever waiting at a baggage carousel.