When sizing a day pack, you want to aim for 20-30 liters of volume in order to carry drinking water, extra clothing, food, and other essentials. The easiest way to decide how much capacity (in liters) you need is to ask yourself how long your hikes will last. Will they be short hikes that are just a few hours in length or much longer, all-day excursions?
Shorter Hikes: 20-25 liter day packs
If your hikes will be less than 4 hours in length (a half-day), you can get a smaller volume daypack closer to 20-25 liters. For hikes close to home or within a reasonable distance to your car, you can usually just bring a map, a hat, insect repellent, sun tan lotion, a camera/phone, some snacks, a bottle of water, a light jacket, and a small first-aid kit if you’ve checked the weather forecast and it’s not going to rain. While you can get something even smaller, you can easily run out of room if you need to carry more stuff.
Here are a few packs that are good for shorter hikes:
Longer Hikes: 26-30 liter day packs
For hikes lasting 6-8 hours or more (a full day), I’d get something larger, in the 26-30 liter range. On longer, full-day hikes, ones farther from shelter, or where weather conditions are more variable, you want to carry all of the above, plus more water, more food, a warmer jacket, a rain jacket, and rain pants, which will be much heavier and require more volume to carry. For example, a liter/quart of water weighs 2 lbs, which really adds up if you carry 2 or 3 liters of water on a longer day hike.
Here are some good packs for full day hikes:
Higher volume daypacks, in the 26-30 liter range also tend to have a stiffer back panel (frame) or even a hip belt so all the weight isn’t on your shoulders but is also carried by your legs. In contrast, small backpacks (in the 20-25 liter range) often lack a hip belt or just come with a webbing strap designed to keep the pack from bouncing against your back when you hike. It varies by make and model, but these are things to look out for.
Winter Day Packs
If you also intend to hike or snowshoe in winter, you might want to get a second, even larger backpack that is between 30 and 40 liters in size. Winter clothing is heavy and bulky while traction aids like snowshoes, microspikes, and crampons are quite heavy. For example, snowshoes weigh between 4 and 5 pounds per pair, so you’ll want a daypack with a frame and a beefier hipbelt that provides more support.
Here are some good packs for winter days hikes:
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