For most overnight hikes, a comfortable backpack in roughly the 35–50 liter range is a practical starting point. The best size depends on how compact your shelter, sleep system, clothing, food, and other equipment are. More important than choosing a particular brand is finding a pack that fits your torso properly, carries your expected load comfortably, and has enough capacity for your gear without being unnecessarily large.
The first time I thought about packing for an overnight hike, I was surprised by how quickly everything added up.
A sleeping bag didn't look particularly large on its own.
Neither did a jacket.
Then came the sleeping pad, shelter, food, water, first aid supplies, spare clothing, and all those little items that somehow appear once you start packing.
Suddenly, choosing a backpack seemed much more complicated than buying something large enough to hold everything.
What I eventually realized is that capacity is only one part of choosing an overnight hiking backpack.
Fit and comfort matter just as much.
The Short Answer
For a typical one-night hiking trip, many hikers can use a backpack around 35–50 liters, although there is no universal perfect size.
You may need less capacity if you have compact, lightweight equipment.
You may need more if you carry:
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Bulky sleeping gear
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A larger shelter
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Cold-weather clothing
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Extra food
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More water
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Specialized equipment
When choosing an overnight hiking backpack, consider:
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Capacity
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Torso fit
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Hip-belt comfort
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Expected pack weight
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Backpack weight
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Organization
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Weather protection
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Ventilation
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Durability
I'd choose the rest of my overnight gear first whenever possible and then select a backpack that carries it comfortably.
1. A 35–50 Liter Backpack Is a Good Starting Point
For a simple overnight hike in moderate conditions, somewhere around 35–50 liters is often a useful range to investigate.
A 35-liter pack can work well when your equipment is compact and you're comfortable packing efficiently.
Moving toward 40–50 liters gives you additional space for bulkier equipment, extra clothing, food, and other necessities.
That doesn't mean a 50-liter backpack is automatically better.
A larger pack can encourage you to bring things you don't actually need.
And once those "just in case" items start accumulating, your comfortable overnight backpack can become surprisingly heavy.
Choose capacity according to your actual equipment rather than simply buying the biggest pack you can find.
2. Fit Is More Important Than the Brand Name
A backpack can have excellent reviews and still be uncomfortable for you.
Bodies are different.
Backpacks are too.
One of the most important measurements is torso length.
Backpack sizing isn't simply based on how tall you are. Two people of the same height can have different torso lengths and therefore prefer different pack sizes or adjustments.
A properly fitted backpack should allow the suspension system and hip belt to work as intended.
That's why I wouldn't choose an overnight pack solely because it's popular online.
If possible, try it with some weight inside.
A nearly empty backpack can feel wonderful in a shop.
Add your overnight equipment and walk for several hours, and you may develop a very different opinion.
3. Look for a Comfortable Hip Belt
On an overnight hike, you'll usually carry considerably more than you would on a short day walk.
That's where the hip belt becomes particularly important.
A well-fitted hiking backpack is designed so that a substantial portion of the load can be supported around your hips rather than hanging entirely from your shoulders.
Look for a hip belt that:
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Fits your body comfortably
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Can be adjusted securely
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Doesn't create painful pressure points
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Works properly with the pack's torso length
Some hip belts also include pockets.
I find these particularly convenient for small items I want while walking, such as:
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Snacks
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Lip balm
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Small sunscreen
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Other frequently used items
The less often you need to remove your entire backpack, the better.
4. Make Sure Your Overnight Gear Actually Fits
Before buying a backpack, think about what you'll put inside it.
Your largest overnight items will usually include some combination of the Big Three:
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Backpack
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Shelter
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Sleep system
The sleep system generally includes your sleeping bag or quilt and sleeping pad.
Then you'll need room for other essentials such as:
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Food
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Water
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Clothing
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Cooking equipment if required
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First aid supplies
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Navigation
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Headlamp
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Hygiene items
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Weather protection
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Emergency equipment
Cold-weather equipment tends to be bulkier than warm-weather gear.
So the same person might comfortably use a relatively small backpack for a summer overnight hike but want substantially more capacity for colder conditions.
Your gear determines the pack.
Not the other way around.
5. Don't Automatically Choose the Lightest Backpack
Lightweight gear can make hiking more comfortable.
But backpack weight shouldn't be considered in isolation.
A very light pack may use a simpler suspension system, fewer features, or lighter materials.
That can work beautifully when the rest of your equipment is also light.
It may feel less comfortable if you load it with heavy, bulky traditional camping gear.
Think about the total load you're expecting to carry.
If your overnight equipment is relatively heavy, you may appreciate a backpack with a more supportive frame and suspension system even if the pack itself weighs a little more.
If you've already reduced your total gear weight considerably, a lighter backpack may make more sense.
Comfort with your actual load is more important than winning a competition over the backpack's empty weight.
6. Decide How Much Organization You Want
Backpacks range from extremely simple to impressively complicated.
Some have one large main compartment.
Others seem to contain enough pockets to lose your belongings in several different locations simultaneously.
Common features include:
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Top lid
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Hip-belt pockets
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Side bottle pockets
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Front stretch pocket
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Internal compartments
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Sleeping bag compartment
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Hydration reservoir sleeve
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Attachment points
Neither approach is automatically better.
I like having easy access to things I'll need while hiking.
For example, I don't want my rain jacket buried underneath my sleeping bag when dark clouds suddenly appear.
Items such as water, snacks, navigation, rain protection, and sunscreen should be relatively easy to reach.
Everything else can be packed according to how often you'll need it.
7. Think About Water Carrying
Before choosing a backpack, check how it handles water.
Many hiking packs have side pockets for bottles.
Some are compatible with hydration reservoirs.
Others support both.
Think about which system you actually prefer.
Also consider whether you can reach your water without removing the backpack.
That may sound like a tiny detail.
After several hours of hiking, it becomes surprisingly important.
Your required water capacity will depend on the route, weather, availability of reliable water sources, and whether you're carrying a treatment method.
Don't choose a backpack assuming you'll always find safe drinking water along the trail.
Research your route beforehand.
8. Consider Weather Protection
Most hiking backpacks shouldn't be treated as completely waterproof simply because they're made from technical fabric.
If you're expecting rain, protect the contents appropriately.
Options can include:
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Backpack rain cover
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Waterproof pack liner
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Dry bags
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Waterproof stuff sacks
For particularly important items—such as your sleeping bag, spare insulation, electronics, or other gear that needs to stay dry—I prefer not to rely entirely on the exterior backpack fabric.
A wet sleeping bag can turn a slightly inconvenient evening into a much more serious problem in cold conditions.
Your weather-protection strategy should reflect the conditions you're hiking in.
9. Ventilation Can Improve Comfort
Backpacks sit against your body for hours.
Naturally, things can become warm.
Many hiking packs use ventilated back panels, mesh, channels, or suspended designs intended to create some airflow between you and the backpack.
No backpack is going to eliminate sweating during strenuous hiking.
But some designs may feel more comfortable than others.
This is another reason trying a backpack can be useful.
One person may love a highly ventilated suspended back panel.
Another may prefer a pack that sits closer to the body and feels more stable.
Comfort is personal.
10. Pack Weight Matters More Than Backpack Size Alone
It's easy to focus entirely on liters.
But a 40-liter backpack containing heavy equipment can be harder to carry than a 50-liter backpack containing lightweight equipment.
Think about both:
Volume — how much space your gear occupies
and
Weight — how heavy everything is
Your food and water can contribute significantly to total pack weight even though they're consumed during the trip.
Before your first overnight hike, pack everything at home and weigh the complete backpack.
Then put it on.
Walk around.
Even better, take it on a shorter practice hike.
You'll learn much more from carrying your actual equipment for an hour than from repeatedly reading backpack specifications.
Should I Get a 40L or 50L Backpack for an Overnight Hike?
Either can work.
A 40-liter backpack can be a good choice when you have relatively compact equipment and are packing for moderate conditions.
A 50-liter backpack gives you more flexibility for bulkier sleeping equipment, additional clothing, colder weather, or simply a less optimized gear setup.
For a beginner buying their first overnight backpack, I wouldn't obsess over the exact number.
Put your equipment together first.
Then estimate how much space it requires.
If your sleeping bag alone occupies an enormous portion of a 40-liter pack, trying to force everything into that capacity probably won't make the hike more enjoyable.
On the other hand, if all your gear comfortably fits into 40 liters, there's little reason to carry a much larger backpack simply because you might theoretically use the extra space.
Is a 30L Backpack Enough for an Overnight Hike?
It can be.
A 30-liter backpack may work for hikers with very compact, lightweight equipment, particularly in mild conditions.
But it can be restrictive for a beginner using conventional camping gear.
Sleeping bags, shelters, insulated clothing, and cooking equipment can take up considerable space.
Trying to achieve an extremely small backpack volume before you've gained overnight hiking experience can also lead to leaving behind useful equipment simply to make everything fit.
I'd prioritize appropriate equipment and safety first.
You can refine your packing system as you gain experience.
What About a 60L Backpack?
A 60-liter backpack isn't automatically too large for an overnight hike.
It may make sense for:
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Cold-weather trips
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Bulky equipment
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Specialized gear
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Trips where you need to carry substantial water
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Longer outings beyond a single night
But for an ordinary overnight trip in moderate conditions, many hikers won't need that much space.
The danger of extra capacity is that empty space has a mysterious tendency to fill itself.
A spare shirt becomes two.
One snack becomes six.
A small "just in case" item appears.
Then another.
Before you know it, you're carrying a much heavier backpack without gaining much practical value.
A Quick Aside About Buying Your Backpack Last
There's a piece of backpacking advice I find particularly sensible:
Choose your backpack after you've chosen most of the gear that needs to go inside it.
If you buy a tiny ultralight backpack first and later discover that your sleeping bag, tent, and clothing are bulky, you'll have a packing problem.
If you buy an enormous backpack first, you may end up carrying unnecessary capacity and filling it with unnecessary equipment.
Get a reasonable idea of your shelter, sleep system, clothing, cooking setup, food, water requirements, and other essentials.
Then find a backpack that accommodates that equipment and carries the expected weight comfortably.
It makes the decision much easier.
My Personal Takeaway
For most overnight hikers, I'd start by looking at backpacks in roughly the 35–50 liter range, with around 40–50 liters often providing a practical amount of space for beginners using typical overnight gear.
But I wouldn't call any particular capacity—or any particular backpack—the universal best.
The best overnight hiking backpack is one that fits your torso and hips properly, carries your expected load comfortably, holds the equipment required for your route and conditions, and doesn't encourage you to carry unnecessary gear.
Choose your overnight equipment first.
Measure your torso.
Try packs with weight inside whenever possible.
Think about water access, weather protection, organization, and the conditions you'll hike in.
Then pack everything at home and take your loaded backpack for a short practice walk.
Because the best backpack isn't necessarily the lightest one, the biggest one, or the most expensive one.
It's the one you can carry comfortably when the trail stops being flat and your campsite is still several kilometers away.