A 30 liter backpack is typically 18 inches tall, 13 inches wide, and 8 inches deep. This size is perfect for carrying around all of your essentials without being too big or too small. If you're planning on using your backpack for hiking or camping, then you'll want to make sure that it has enough space to hold all of your gear. A 30l backpack should have no problem fitting everything you need for a weekend trip. So, if you're looking for a versatile and spacious backpack, then you should definitely consider getting a 30l bag.