A well-packed backpack covers ten functional categories: navigation, sun protection, insulation, illumination, first aid, fire, repair tools, nutrition, hydration, and emergency shelter. This system, maintained by the U.S. National Park Service, applies whether you’re heading out for a three-hour day hike or a multi-day trek. The specific items you bring will scale with your trip length, but the categories stay the same.
Water and Hydration Supplies
Water is the heaviest and most critical thing in your pack. A good baseline is about half a liter per hour of moderate hiking in moderate temperatures. In high heat or on steep terrain, that can jump to a full liter or more per hour. For a four-hour day hike on a warm day, plan on carrying at least two liters, and more if there’s no reliable water source along the route.
Beyond the water itself, carry a way to treat water you find on trail. A compact filter, purification tablets, or a UV purifier lets you refill from streams without carrying your entire day’s supply from the trailhead. This matters most on longer hikes where carrying eight or ten pounds of water from the start isn’t practical.
Food and Trail Nutrition
The goal with trail food is maximizing calories while minimizing weight. Aim for foods that deliver at least 100 calories per ounce, with 125 or more being ideal. Nuts, nut butters, dried fruit, energy bars, cheese, and chocolate all hit that range. Dehydrated meals work well for multi-day trips since you’re only carrying the dry weight.
Balance carbohydrates for quick energy, protein for sustained effort, and fat for caloric density. A mix of salty and sweet snacks that you can eat without stopping keeps your energy steady throughout the day. Always pack more food than you think you’ll need. An unexpected delay or wrong turn can add hours to your trip.
Navigation Tools
At minimum, carry a paper map and a compass. Phone batteries die, GPS signals drop in canyons and dense forest, and electronics fail in rain. A compass with a declination adjustment lets you translate between the map and the real world without doing math in your head to account for the difference between magnetic north and true north.
A smartphone running a GPS navigation app like Gaia GPS is a powerful complement to paper maps, not a replacement. The biggest advantage of a GPS-enabled device is that it can show you exactly where you are and where you’ve been, something a compass alone can’t do. Keep your phone in airplane mode to conserve battery, and consider carrying a small power bank.
Experienced hikers often carry two or three paper maps from different sources. Hiking-specific maps sometimes omit ski trails, logging roads, or fire lanes that intersect your route, and trails get rerouted or closed without maps being updated. Having a second map from a different publisher fills in those gaps.
Clothing and Insulation
Weather in the mountains can shift from sunshine to freezing rain in an hour. Your insulation system should include a lightweight jacket, a rain shell, a warm hat, and gloves, even on summer day hikes. The combination of wind and wet clothing can cause hypothermia at surprisingly mild temperatures.
For base layers and socks, the choice comes down to merino wool and synthetics like polyester. Synthetics wick moisture faster and dry quicker, making them better for high-intensity activities in wet conditions. Merino wool absorbs moisture more slowly but continues to insulate when wet, resists odor far better, and regulates temperature across a wider range. For multi-day trips or cooler weather, merino is hard to beat. For hot, sweaty day hikes, synthetics have the edge.
Avoid cotton entirely. It absorbs sweat, loses all insulating ability when wet, and takes hours to dry.
Sun Protection
Sunburn is one of the most common trail injuries, and UV exposure at altitude is significantly stronger than at sea level. Carry sunscreen, sunglasses, and a hat with a brim.
UV-protective clothing actually outperforms sunscreen in lab testing. A study published in the National Center for Biotechnology Information compared modern sun-protective fabrics against SPF 30 and SPF 50 sunscreens and found that all four fabrics blocked both UVB and UVA radiation more effectively than either sunscreen. People also tend to apply sunscreen too thinly, further reducing its real-world effectiveness. The practical takeaway: cover as much skin as possible with clothing first, then use sunscreen on exposed areas like your face, neck, and hands.
First Aid Kit
Your first aid kit doesn’t need to be elaborate, but it does need to cover the injuries that actually happen on trail. Blisters, small cuts, sprains, and splinters account for the vast majority of hiking injuries. The American Red Cross recommends building your kit around these core supplies:
- Wound care: adhesive bandages, antiseptic wipes, antibacterial ointment, gauze pads, medical tape, and closure strips for deeper cuts
- Blister treatment: moleskin or hydrogel-based pads (apply these at the first sign of a hot spot, not after the blister has formed)
- Musculoskeletal injuries: an elastic wrap for sprains, a SAM splint that can be shaped to any limb, and a triangular bandage for making a sling
- Extras: tweezers for splinters and ticks, non-latex gloves, pain relief medication, and any personal prescriptions like an EpiPen or inhaler
Check your kit before every trip. Ointments expire, adhesives lose their stick in heat, and supplies used on your last hike may not have been replaced.
Illumination and Fire
A headlamp is essential even on day hikes. Trails take longer than expected, ankles get twisted, and suddenly you’re navigating back to the trailhead in the dark. A headlamp keeps your hands free for scrambling and using trekking poles. Carry spare batteries or choose a rechargeable model and top it off before you leave.
Fire-starting supplies serve both warmth and signaling purposes in an emergency. Carry a lighter (the most reliable option), waterproof matches as backup, and a small amount of fire starter material like cotton balls coated in petroleum jelly. These weigh almost nothing and can be the difference between a cold, uncomfortable night and a survivable one.
Emergency Shelter
Even on day hikes, an emergency shelter belongs in your pack. An emergency bivy or space blanket weighs under four ounces and can prevent hypothermia if you’re stuck overnight. These work by reflecting your body heat back toward you while blocking wind and rain. A lightweight tarp with a few feet of cord offers more versatile protection and can double as a rain cover for your gear.
Repair Tools
A small knife, a few feet of duct tape wrapped around a pencil or water bottle, and a length of cord handle most on-trail gear failures. Duct tape patches torn rain shells, fixes delaminating boot soles, and even works as blister tape in a pinch. A multi-tool with a blade and small scissors covers cutting tasks without adding much weight.
Managing Pack Weight
How much you can comfortably carry depends on your body weight and fitness level. The old rule of thumb that everyone should carry no more than 20% of their body weight is an oversimplification. Research on hiking biomechanics shows that a lighter person (around 112 pounds) may safely manage up to 45% of their body weight, while a heavier person (around 243 pounds) might find 14% of their body weight to be their practical limit. The relationship between body size and carrying capacity isn’t linear.
For most day hikers, the pack will weigh somewhere between 10 and 20 pounds including water and food. If your pack feels heavy, prioritize cutting weight from your heaviest items first: water (carry treatment instead of extra water when sources are available), food (choose calorie-dense options), and shelter or extra clothing. Shaving an ounce off ten small items matters less than saving a pound from one big one.
Pack heavy items close to your back and centered between your shoulder blades and hips. This keeps the weight over your center of gravity and reduces strain on your shoulders and lower back. Adjust your hip belt so it carries 60 to 70 percent of the load on your hips rather than your shoulders.