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About this tool
Build a backpacking list as a weight budget: base weight, food by calorie density and water, checked against 20% of your body weight.
The Backpacking Packing List Builder treats a backpacking list as a weight budget rather than a checklist. It separates base weight — everything that is not eaten, drunk or burned — from consumables, sizes food by calorie density at the classic 125 kcal per ounce (4.4 kcal per gram), counts water at 1 kg per litre, and checks the loaded total against the 20%-of-body-weight carrying guideline. The sleep system is chosen from the expected night low using the ISO 23537 comfort rating rather than the survival limit printed on the label.
Open Backpacking Packing List Builder on AltFTool — it loads instantly in your browser.
Enter Nights out, Your body weight (kg), Expected night low (°C) and Daily energy target (kcal).
Set Water carried between sources (L), Resupply every N days (0 = none) and Tent shared between, then tick the Conditions: Rain expected, Cooking on a stove, Trekking poles.
Read Base weight (no food, water or fuel) against the 20% target for your body weight, plus Food carried, Water carried and Sleeping bag comfort rating, then press Copy list.
Consumables shrink as you walk; base weight is the number you can actually change.
Enter a daily calorie target and get grams, not a vague 'a kilo a day'.
Mid-layer, puffy, waterproofs and mat thickness all switch on from the night low.
The common guideline is no more than 20% of your body weight fully loaded, so 14 kg for a 70 kg hiker, and 10-15% if you are new to carrying a load or the terrain is steep. Food, water and fuel are usually a third of that, which is why they are counted separately here.
Base weight is the weight of your pack with everything in it except consumables — no food, water or fuel. It is the number that stays the same on day one and day six, so it is the only part you can reduce by choosing different gear. Under 9 kg is generally called lightweight and under 4.5 kg ultralight.
Plan by calories, then convert: at the standard target of 4.4 kcal per gram (125 kcal per ounce), a 3,000 kcal day weighs about 680 g. If your food bag weighs much more than that per day, it is carrying water — swap fresh items for dried ones rather than eating less.
Use the ISO 23537 comfort rating, not the extreme or limit figure, and pick one at or a few degrees below the expected overnight low. A bag whose comfort rating equals the forecast leaves no margin for a colder night, a damp bag or a tired body, so this tool suggests about 5 °C of headroom.