Packing by Category vs. Packing by Day: Which System Works Better
Organizing by category (all tops together, all toiletries together) makes it easier to check for completeness within each type of item and pack efficiently by category. Organizing by day (what's needed for day 1, day 2) makes it easier to plan a specific outfit or itinerary-based need for each day, but can make it harder to spot a category-wide gap (like realizing no rain gear was packed at all).
Neither system is universally better — they suit different planning styles and different types of trips.
Category-based organization
Grouping items by type (all clothing, all electronics, all toiletries) makes it straightforward to check whether an entire category has been adequately covered, and tends to pack more efficiently into luggage, since similar items naturally group together — this system is generally well suited to trips without a highly structured day-by-day itinerary.
Day-based organization
Planning specifically what's needed for each individual day works well for a trip with a detailed, activity-specific itinerary (a formal event on day 3, a hike on day 5) — it directly ties packing to the actual planned schedule, though it can make it harder to notice a category-wide gap that spans the whole trip rather than being tied to a single day.
Combining both approaches
Building the list by category first (to ensure complete coverage of each item type) and then cross-checking against a day-by-day itinerary (to confirm each day's specific needs are covered) combines category organization's completeness check with day-based organization's itinerary alignment.