Plan the legs, not the trip
Total food weight for a three-week route is a number nobody ever carries and it tells you nothing useful. The number that decides how the trip feels is the heaviest single leg, and that is a route-planning choice rather than a food choice. Two hikers with the same daily calories on the same trail can have longest carries of four days and eight days depending only on which towns they choose to stop in, and the second one is walking with four extra pounds on the section where the pack is already heaviest.
The calculator makes that visible by splitting at each point you list and weighing each leg separately. Adding a resupply in the middle of a long gap usually costs half a day of walking and takes several pounds off the worst carry, and whether that trade is worth it is a judgement — but it is much easier to make with both numbers in front of you.
Calorie density is the whole game
| Roughly | Calories per ounce | What that means for a 3,000 kcal day |
|---|---|---|
| Fresh produce, tinned food | 10 to 30 | Unworkable to carry; fine for the first evening out |
| Bread, tortillas, crackers | 75 to 110 | Around 2 lb a day on its own |
| Typical mixed trail food | 110 to 130 | About 1.5 lb a day |
| Bars, dried meat, cheese | 120 to 160 | Around 1.3 lb a day |
| Nuts, nut butter, oils | 160 to 250 | Under 1 lb a day, and unpleasant as the whole diet |
The ratio between the top and bottom of that table is enormous, and it applies to every day of the trip at once. Someone packing at 100 calories an ounce carries 1.9 pounds a day; at 140 it is 1.3. Over a seven-day carry that is nearly four pounds, which is more than most people ever save on gear. This is also the reason the classic advice about fat is arithmetic rather than nutrition: fat carries roughly twice the calories per gram of protein or carbohydrate, so a food with more of it is denser almost by definition.
Where it stops being arithmetic is that food nobody wants to eat does not get eaten. A pack that comes out of a leg with two untouched days in it was carrying two days of dead weight, and the hiker was short on calories the whole time. Density is a lever with a real limit and the limit is personal.
The spare day is not free
Half a day or a full day of extra food on every leg is sensible, and on a route with six resupply points it is three to six days of food bought and carried over the trip. It is worth knowing that number rather than adding it by reflex, because it is the line that repeats. Some people carry a full spare day on remote legs and nothing on the ones that end at a road. That is a per-leg decision the total does not show.
Resupply points are not all the same thing
A full grocery store, a gas station with a shelf of snacks, a post office holding a box you packed at home and a hostel that accepts packages are four different things pretending to be the same dot on a map. The gas station will not sell you four days of anything you want to eat. The post office has hours, and they are not the hours you will arrive. Boxes solve the selection problem and create a scheduling one. None of that is arithmetic, but it changes which legs are actually possible, so it belongs in the planning before the weights do.
Questions people ask
How many pounds of food per day for backpacking?
It falls straight out of two numbers: your daily calories and the calorie density of what you pack. At 3,000 calories a day and 125 calories an ounce it is 24 ounces, or 1.5 pounds. At the same calories and 100 calories an ounce it is 1.9 pounds; at 150 it is 1.25. The often-quoted one-and-a-half to two pounds a day covers the middle of that range and hides which of the two inputs is driving it.
What calorie target should I use?
Your own, and it should come from your own experience on similar days or from a dietitian or doctor who knows your situation. What a specific person burns walking with a pack depends on their body, the terrain, the weather and the load, and none of that is something a web page can assess. The field here takes whatever figure you supply and multiplies it by days. It does not suggest a value and it makes no judgement about whether the result is enough.
How do I work out the calorie density of my food?
Take the calories on the label and divide by the ounces in the package, using net weight rather than the pack size. Do it for a representative week of what you actually pack, including the packaging you carry, and average it. Most people find their real figure is lower than they expected, because the bars and nut butter they think of as typical sit alongside a lot of heavier things they forget about.
Should I mail resupply boxes or buy in town?
Boxes give you exactly the food you planned and fix the price, and they tie you to post office hours and to a schedule you set months earlier. Buying in town gives flexibility and variety and puts you at the mercy of whatever the shop stocks, which in a small trail town can be very little. The common approach is to buy where there is a real grocery store and mail boxes only to the places where there is not. Confirm with the receiving business or post office that they will hold a package before you send it.
How much extra food should I carry?
Enough to absorb the delays you consider likely on that particular leg, which is a different answer on a remote high traverse than on a section that crosses a road every day. Half a day to a full day per leg is common. What the calculator adds is visibility of the total: on a six-leg route, a full spare day each time is six days of food bought and carried, which is a meaningful weight and cost that never appears as a line item anywhere else.