Check a camping gear packing list.
Gear lists split into two categories that scale differently, and conflating them is why packing lists go wrong. Shared group kit — tent, stove, water filter, first aid, repair kit — is counted once no matter how many people come, so a car-camping group needs around 22 shared items whether there are two of you or six. Per-person kit scales with head count and rises sharply with trip severity: backpacking needs more individual items than car camping because everyone carries their own everything, and winter camping needs more again for insulation and avalanche safety. Trip length adds only clothing changes, capped since you begin rewearing and washing.
Required items
Required = shared kit + per-person kit x group size + clothing extras
Completeness
Completeness % = items packed / required x 100
A planning aid only, not a safety certification. An item count cannot verify that you have the right gear for the conditions, that it is in working order, or that you know how to use it. Check the forecast, leave your route with someone, and carry appropriate navigation, shelter and first aid for the terrain and season.
Because nothing can be shared out of a boot. Each person carries their own pack, sleep system, water treatment, rain shell and headtorch, and there is no vehicle to fall back on. The shared list is shorter because weight forces you to leave the luxuries behind.
Shelter, an adequate sleep system for the expected low temperature, water treatment, navigation, a headtorch, insulation, and a first aid kit. If any of those is missing the count is irrelevant — those seven categories are what separate an uncomfortable night from a genuine emergency.