Check backpack weight against body weight.
Pack weight is conventionally judged as a share of body weight, with about 20 percent the accepted ceiling for multi-day hiking and 25 percent the point where injury and fatigue risk rise sharply. The figure that matters is total weight, which means base weight plus consumables — and consumables are where packs get heavy. Water is the worst offender at a full kilogram per litre, so carrying four litres adds four kilograms, which is often more than a tent. Food at 700 grams a day compounds with trip length. This is why the same base weight is comfortable on a two-day trip and punishing on a seven-day one.
Total weight
Total kg = base weight + days x food per day + litres of water
Body weight share
Share % = total pack kg / body weight kg x 100; recommended max = 20% of body weight
General guidance for recreational hiking, not medical or safety advice. Safe carrying capacity varies with fitness, terrain, altitude, age and injury history, and children should carry substantially less. Consult a qualified professional if you have a back, knee or joint condition before carrying a loaded pack over distance.
It weighs a full kilogram per litre and there is no lightweight substitute. Four litres is four kilograms — heavier than many tents. Carrying only what you need to reach the next reliable source, and using a filter rather than hauling a full supply, is usually the single biggest weight saving available.
Base weight is everything except food, water and fuel — the part that does not change with trip length. It is the honest measure of your kit choices, because it lets you compare setups without a long trip's consumables masking the difference. Under 9 kg is considered lightweight.