Background: Why the question of kilos is confusing

Volume in liters and mass in kilograms are often confused. Filling 40 liters of water would result in 40 kg, well beyond what a 40-liter backpack and harness can comfortably support. In practice, we carry objects of varying densities, and the actual limit depends on your body, the terrain, and the quality of the carry.

Recommendations converge around 10 percent of body weight for a day trip and around 20 percent for several days if the bag is properly adjusted. Hence the idea that a well-designed and well-adjusted 40 L bag often carries 8 to 12 kg without discomfort.

Step-by-step method for sizing and packing a 40 L

Step 1: Set a realistic target load

Calculate a simple target weight x 10 percent for the day or x 20 percent for the bivouac. For example, 70 kg gives 7 kg for the day or up to about 14 kg for a trek. Take this as a ceiling, not a goal.

• Day at most 10 percent of your weight.
• Trek at most 20 percent to be adjusted if there is a steep gradient or heat.
• Your condition and experience take precedence over any magic ratio.

Step 2: Choose a 40L bag that really carries

Not all 40L bags are created equal. A lightweight internal frame, rigid waist belt , and ergonomic shoulder straps transfer 60 to 80 percent of the load to the hips. Look for a stable back and effective load-retaining features.

• Belt that rests on the hip bones.
• Adjustable load reminders towards the shoulders.
• Anchor points and straps to prevent swinging.

Step 3: optimize the three large sleeping shelter and carrying positions

This trio weighs the most. Switching from a standard combo to lighter versions often saves 1.5 to 3 kg.

• Shelter at most 1.5 kg depending on the season.
• 3-season duvet or quilt around 700 to 1000 g.
• Mattress with R value suitable for insulation of at least 3 for three seasons.

Step 4 water and food density and autonomy

Water weighs 1 kg per liter. Carry only the necessary volume between two reliable points. For food, plan on 500 to 800 g per day per person with high energy density.

• Identify water points on the map with filter or treatment.
• Rations 2800 to 3500 kcal per day depending on effort and size.
• Avoid metal cans and heavy liquids.

Step 5: Distribution and adjustments to relieve back pain

Place dense items against your back and vertically centered, bulky items at the bottom and top, and water close to your body's center. Tighten the waist belt first, then adjust the shoulder straps and chest strap.

Example figure 40 L for 2 days and 1 night approximately 10.4 kg

Profile 70 kg, ceiling 20 percent approximately 14 kg, comfort target 9 to 11 kg.

• Shelter 1 to 2 places 1300 g and sardines 120 g
• 900g 3-season duvet and 450g mattress
• Clothing 900 g
• Stove and cooking pot and gas 450 g and lighter 15 g
• Food 2 days 1400 g approximately 700 g per day
• Water 1.5 L equals 1500 g depending on water points
• Pharmacy and tools and electronics 600 g
• 40 L bag with frame 1250 g

Indicative total approximately 10.4 kg depending on season and equipment.

Frequent risks and countermeasures

1 chronic overweight

Frequently exceeding 20 percent of your body weight increases fatigue and risks. Reduce heavy items and water intake first.

2 bad distribution

A center of gravity away from the back pulls on the shoulders. Place dense and heavy items against the back panel, centered vertically.

3 unsuitable harnesses

Soft belts and thin straps don't transfer the load to the hips. Choose a firm belt if you're aiming for 10 to 12 kg.

Equip smartly with Arknor

To compose a 40 L balance, start with these categories from the Arknor site.

• Backpacks 20 to 40 L
• Sleeping bags and insulated mattresses
• Tents and tarps
• Stoves and combustion
• Navigation and orientation

To go further Minimalism in bivouac and 10 bivouac errors .

FAQ quick answers

Is a 40 L enough for 3 to 4 days?

Yes, if you stay organized and keep your shelter light: no more than 1.5 kg, down no more than 1 kg, dense rations, 1 to 1.5 L of water between reliable points.

What is the maximum weight to aim for in a 40 L?

For most body types, 8 to 12 kg is comfortable. Avoid exceeding about 20 percent of your body weight over several days, and stay under 10 percent during the day.

How to distribute the load in the bag

Heavy objects against the back and vertically centered, compressible at the bottom and top, water close to the axis. Adjust the waist belt first and then the rest.

Sources and image credits

• REI Expert Advice charges daytime travel about 10 percent and trekking about 20 percent REI Advice Sheet
• Decathlon bag adjustment and distribution Bag adjustment guide
• Montania Sport Weight and Volume Reflections Article
• Mammut marks 10 percent day and 20 percent trek Mammut Guide
• Water density 1 kg per liter Converter L to kg
• Images Wikimedia Commons CC BY SA see credits under each figure