There are different types of hiking backpacks of various sizes and dimensions. As long as your hiking backpack meets the airline regulations regarding size and weight, you should be allowed to bring your backpack onboard as a carry-on.
However, most likely you are referring to hiking backpack that is more than 40L and quite large in size such as 70Liters +. In such a case, you will not be able to bring it on as a carry-on.
Most airlines won’t allow you to bring a hiking backpack like this as a carry on! It’s too big!
Most common size carry-on in USA
22 x 14 x 9 inches or 56 x 35.5 x 23 centimeters is the most common carry-on luggage limit. However, higher end airlines like Southwest are generous with the size, so use the picture below for some reference.
Usually, carry on backpacks should not exceed much more than a 40 liter backpack.
On a 5’10\” 178cm man, the maximum limit for a backpack that is allowed on a plane will look something like this.
Depending on the airline worker’s discretion, you could get away with a slightly bigger hiking backpack, as long as it looks visually around the same ballpark as the picture above.
However, you’re still rolling the dice in such cases.
What about non-USA carry-on size limit?
The world standard should be more or less around that size, but it’s always a good idea to check with your specific airline for their rules and regulations to be fully sure.
Is there a weight limit for carry-on backpacks?
A good rule of thumb is to not exceed 15 pounds or 7 kilos, but some airlines such as Delta etc don’t have specific weight restrictions, so always check with your carrier airline.
If you exceed the weight limit, you could get away with it if your carry-on bag is small enough to pass as a personal item, like a small backpack. Sometimes the airline workers don’t bother to check the weight. However, sometimes airline workers CAN ask you to put your backpack on the scale to determine the weight, so it depends…
If your hiking backpack is a lilttle larger and heavier but still around the general ballpark, you could be allowed to board without any problems. Worst case scenario is that you will have to pay a little extra if your bag gets checked for weight and dimensions.