You are reading a tutorial on how to use caloric density to calculate meal plans and rations for backpacking. If you haven’t already, open up my table of caloric densities by clicking here so you can follow along.
Why take the time to calculate your daily caloric expenditure and intake? There are several reasons, let me enumerate them:
- To be aware of how much energy you’re expending and how much you’re putting in and, therefore, avoid carrying excess or stretching yourself thin.
- To better minimize the amount of food weight carried between resupplies. In other words, to become more efficient.
- To increase your personal awareness of what you’re carrying.
How Many Calories Will I Burn?
In order to do this we’re first going to need to get a rough estimate of how many Calories (see my article on caloric density for the difference between Calories and calories).
There are a few sources of reference I’ve been able to find and use as a judgment of caloric expenditure on extended backpacking trips.
Andrew Skurka, a long distance backpacker whose judgment I find very sound, plans 5,000+ Calories a day when hiking 30+ miles. I paraphrase his words, but you can find his information on his site and in his book The Ultimate Hiker’s Gear Guide. The book is well worth your time as are many of his articles on his site.
Another reference for calories burned while backpacking is NutriStrategy’s site. I’ve stumbled across their numbers before and, to be honest, I have no idea at all how they came up with the numbers on their list. However, doing a quick computation it seems their numbers are reasonably within the ballpark of what I’d expect. Use them as reference for rough computations.
The final source of reference for caloric expenditure should be your own personal experience. Sites like Whiteblaze.net are full and overflowing with hikers (and forum lurkers who think they’re hikers) more than happy to regurgitate numbers at you from their experience as well. Take it with a grain of salt.
Now let’s get down to it. For the sake of this tutorial we’re going to plan a diet of 4,500 Calories per day while backpacking 25 miles a day over mountainous terrain at low elevation (Appalachian Trail).
You’ve got the list of caloric densities open, don’t you? Good, let’s continue.
We’ll start simple. Let’s figure out how many ounces of Sun Chips we need to eat to provide our daily 4,500 Calories. In order to do this we are going to divide our daily total by the caloric density of Sun Chips (140 Cal/oz).
4,500 Calories /140 Calories per Ounce = 32.14 oz
Algebra tells us that the unit “Calories” in this equation cancels out and the number we’re left with is simply ounces. So we would need to eat 32.14 ounces, almost exactly two pounds, of Sun Chips to meet our intake goal.
You might see the problem with this by now. We can’t eat just one thing and, often, there will be multiple ingredients in each meal. So how do we calculate this increasingly complex number?
Breaking it Down by Meal
We need to know the caloric density of every ingredient we’re using to make our meals and we need to know precisely how much of that ingredient we’re using. Don’t worry it’s simpler than it sounds.
One possible GORP recipe.
Above is a simple GORP recipe with some high caloric density foods. Caloric yield of each ingredient is calculated by multiplying caloric density (cal/oz) by the total ounces of the ingredient in the recipe. Then add up the total weight of all ingredients as well as the total number of Calories in the meal. Finally, divide total Calories by total meal weight for an overall meal caloric density.
Were we to eat nothing but this GORP, we could get 4,500 Calories per day by carrying a meager 27.6 oz of food.
Determining Target Caloric Density
Use the table below to decide what caloric density seems right for you.
- Weight (oz) needed per day for each given caloric density.
This table was made to solve for caloric density given a target intake and total daily weight. Ideally I’d like to carry as little food as possible to achieve my 4,500 Calories for the day. So at 32 oz (the chart doesn’t go below two pounds of food per day) I’d need an average meal density of 140-145.
Alternately, let’s say you know your daily caloric requirement is 4,500 and your average meal density is 120. Simply go to the 120 cal/oz row and find the column of daily weight corresponding to 4,500 Calories. In this case it’s somewhere between 36.8 and 38.4 oz. You could, of course, divide 4,500 by 120 to get an exact number (37.5).
Now we know we need to shoot for an average meal density of 140-145 Cal/oz in order to reach our 4,500 Cal/day at a total daily food weight of 2 pounds (32 oz).
Now let’s use all these numbers to help plan my Appalachian Trail thru hike.
Without ever having to travel more than .6 miles from the trail head (only in two locations do I actually have to leave the trail to resupply) my second longest stretch between resupplies is 132 miles (followed closely by 136 miles for the longest). Resupplying as close as possible to the trail allows me to continue moving and avoid expensive trips in to town.
For this section I’ll need 4 full days of food, plus one dinner the night I pick up resupply, and breakfast + lunch the day of my next resupply. Using our 4,500 Calories per day as a baseline at 145 Cal/oz average meal density I need 31 oz of food each full day. Plus the individual breakfast, lunch, and dinner on resupply days which conveniently works out to an extra full day of food.
31 oz per day X 5 full days = 155 oz
For this section I’ll need to plan 9.7 pounds of food (155 oz).
Using Percentages to Plan Backwards
So how do we know exactly how much of each meal to pack?
Let’s go back to our GORP recipe.
One possible GORP recipe.
Let’s say I know my breakfast and dinners together give me 2,000 Calories, and I have a power bar that will supply 400 Calories around lunch time. The rest of the day I’d like to fill in with my mixed GORP recipe. That’s 2,400 Calories of my daily 4,500.
4,500 Cal – 2,400 Cal = 2,100 Cal
I’m left with 2,100 Calories to supplement with my GORP mix. Let’s figure out how much of each ingredient we need to mix up in order to make ends meet on this day. Remember our GORP has a caloric density of 162.98 (we’ll use 163 here for sake of argument).
2,100 Cal / 163 Cal per oz = 12.9 oz
We need 12.9 oz of GORP to make up the difference in our daily meal plan.
For the final step, we need to determine the ratios of our GORP ingredients. We can do this by dividing each ingredient’s individual weight by the combined meal total weight.
Macadamia Nuts: 1 / 7 = 14.3%
Pecans: 1 / 7 = 14.3%
Chocolate Chips: 1 / 7 = 14.3%
Sun Chips: 2 / 7 = 28.6%
Fritos: 2 / 7 = 28.6%
Now we can take the 12.9 oz total we came up with earlier and multiply it by these percentages. Remember 14.3% is (.143) and 28.6% is (.286).
Macadamia Nuts: 12.9 oz X .143 = 1.84 oz
Pecans: 12.9 oz X .143 = 1.84 oz
Chocolate Chips: 12.9 oz X .143 = 1.84 oz
Sun Chips: 12.9 oz X .286 = 3.69 oz
Fritos: 12.9 oz X .286 = 3.69 oz
The obvious, and much simpler solution to this problem, would be to mix up a huge batch of GORP to the ratio you need and then just weigh out 12.9 oz. There will be times, however, when you need to plan backward like this to fill in the gaps.
I’d like to point out that the math in this article contains a LOT of rounding, while I did round correctly there may still be some finite slippage. For your own calculations remember that .5 and up rounds up, .4 and below rounds down.
Lastly, I’d like to thank you for taking the time to read to this point and I sincerely hope this helps you plan whatever trip you’re about to set out on.