Bug-Out Bag Weight Calculator (72-Hour Kit, Pack Limits & Priorities)
Build a 72-hour emergency kit you can actually carry: the pack weight limit from your body weight and fitness, typical weights for water, food, shelter, clothing, first aid, tools and documents, how many hours a day of walking that weight allows, what to cut when it is too heavy, and a car-kit versus carry-kit split.
How it works
pack limit = body weight × 15–25% by fitness · water 1 kg per litre + 0.3 kg bottles/filter · food ≈ 0.55 kg per day (2,000 kcal dense) · shelter/clothing/fuel by season · sustainable walking ≈ 8 h/day at 15% body weight, −0.2 h per extra percentage point, × terrain factor
A bug-out bag fails in the first kilometre if it is too heavy, so the design starts from the body that has to carry it — a fifth of body weight for an ordinary adult, less for the unfit or injured — and works backward through the categories, where water and shelter dominate and gadgets add up quietly. Since water weighs a kilogram a litre, the biggest saving is carrying a day's worth plus a filter rather than three days of it, and since the load sets how many hours a day can be walked, the same arithmetic tells how far the kit can realistically take you. What will not fit on your back belongs in the car and the house, in tiers.
Worked example
A 75 kg adult of average fitness has a 15 kg limit. A temperate three-day kit with 3 L of water, food, tarp shelter, layers, stove, first aid, electronics, tools, hygiene and documents comes to about 13.3 kg — and carrying a young child's extras adds 2.4 kg for 15.8 kg, 21% of body weight, just over the 15 kg limit. On mixed trails that still allows roughly 6 hours and 20 km a day; dropping to 2 L of water plus a filter saves a kilogram and brings it back under.
Frequently asked questions
Three days or longer?
Seventy-two hours is the standard because most disasters see aid or a return home within that window; the bag should also hold the means to extend it — a water filter, a way to make fire and to signal. Beyond three days, weight forces you toward resupply and vehicles, not a bigger pack.
What do most people forget?
Prescription medications and spare glasses, cash in small notes, paper copies of documents, a charger cable for the phone you actually own, socks, and something for morale — a deck of cards, a child's toy. And they never carry the packed bag until the day they need it.
Related calculators
Emergency-planning figures based on FEMA, Red Cross, CDC and extension-service guidance. Local hazards, official evacuation orders and building codes take precedence — this is a planning aid, not a substitute for them.