Camping Supply Calculator

Packing for a group is a multiplication problem, and the thing people get wrong is which number to multiply by. Almost everything scales with person-days, not with nights: a three-night trip is four days of eating, so a party of four needs sixteen person-days of food and water, not twelve. That one-day offset is why groups run short on the last afternoon.

The quantities this calculator works from

Person-days = People × (Nights + 1) Food = Person-days × 2 lbs + 10% margin Water = Person-days × 1 gallon Tents = People ÷ sleeping capacity per tent, rounded up

Water is the one worth being careful about. A gallon per person per day is the standard car-camping figure and it covers drinking, cooking and washing up. Drinking alone is closer to half of that, so if you are camping somewhere with a tap you can carry far less. If you are not, a gallon of water weighs 8.3 lbs, and four people for three nights is 16 gallons, or 133 lbs of water. That is the number that decides whether you are car camping or backpacking, and it is why filters exist.

Hot weather pushes consumption up by roughly a quarter. Cold weather pulls it down, though not as far as people assume, because dry winter air and heavy exertion both cost you fluid you cannot feel yourself losing.

Food, honestly. Two pounds per person per day is a reasonable planning weight for ordinary camp cooking, and the 10% margin exists because a delayed trip is miserable and a lost meal is worse than a carried one. Backpackers cutting weight run 1.5 lbs of dense calories instead; car campers bringing a cooler routinely exceed 2.5 lbs and do not care.

Fuel is where most estimates go wrong, usually by a factor of several. A standard 8 oz isobutane canister gives roughly an hour of burn time and boils somewhere near 12 to 15 litres of water. Boiling water for freeze-dried meals and hot drinks uses about a litre per person per day, so one canister covers a good many person-days. Actual cooking, simmering, frying, heating a pan of washing-up water, burns through it several times faster. Pick the cooking style above and the calculator uses a realistic ratio rather than assuming the worst.

Never leave behind:

• Navigation (map + compass or GPS)
• Sun protection (SPF 30+, sunglasses, hat)
• Insulation (extra layer, emergency blanket)
• Illumination (headlamp + spare batteries)
• First aid kit
• Fire starter (lighter + waterproof matches)
• Repair tools (multi-tool, duct tape)
• Nutrition (extra emergency snacks)
• Hydration (water + purification)
• Emergency shelter (bivy or space blanket)

That list is the Ten Essentials, and the reason it survives unchanged decade after decade is that every item on it is for the trip that goes wrong rather than the trip you planned. The headlamp matters on the night you misjudge the daylight, not on the four nights you did not.

If you are carrying it all on your back, the quantities above become a weight problem rather than a shopping list. The usual guidance is to keep a loaded pack at or below 20% of your body weight, or up to 25 to 30% if you are conditioned for it. Food at 2 lbs per person-day and water at 8.3 lbs per gallon dominate that total, which is why backpackers plan around water sources instead of carrying the full supply.