Through an ancient village gate on the trail from Lyon to Le-Puy, France 2009.

Making Light ~ Expendables

Determining consumption rate

“Expendables” are the things you carry that disappear over time as you use them. I think of “Consumables” as those supplies used in a single day, such as snacks or a picnic lunch. Buy them on your way out of town, and finish them before reaching today’s destination.

Expendables, on the other hand, are depleted at a more or less daily rate over time – things like medications, toothpaste, antiperspirant, sunscreen, and first aid supplies – for the most part, items that make up your personal, medical, toiletry, blister, and first aid kits. For many of these supplies, you can determine very accurately how much you’ll need for a given period of time, and thereby start off with no more than you’ll need. The perfect expendables list will be consumed during your trip, day by day, and exhausted on the last day.

Other supplies require a bit more effort to minimize accurately. Here’s a way to determine how much you’ll need of various expendables, using toothpaste as an example:

1. Weigh a tube of toothpaste, to the nearest gram. It doesn’t need to be full, but it shouldn’t be too close to empty. This is the“STARTING WEIGHT”.

2. Mark the date on the tube with indelible ink, such as with a Sharpie®.

3. Brush your teeth as you normally do, for several days, preferably at least 10 days, the more the better. Use the same tube each time, i.e., If you brush your teeth after lunch at work, bring the same tube with you to work. (Hey, that’s like practicing not leaving something behind – you’re already almost on the road!).

4. Weigh the tube again. This is the“ENDING WEIGHT”.

5. Calculate the test duration. If you start on February 4th, and stop on the 20th (inclusive), the number of days equals “20 minus 4 plus 1”. (Or just count the days on a calendar). In this example, the number of days is 17. This equals “DAYS”. It doesn’t make too much difference how many days you run a test, but the longer it is, the better you’ll average out day to day variations.

The “TEST TOTAL” equals “(STARTING WEIGHT minus ENDING WEIGHT) divided by DAYS”.

This ignores the weight of the tube or container and determines solely the weight of toothpaste you use per day. Let’s say the weight on February 4th was 192 grams, and the weight on February 20th was 146 grams. That means the TEST TOTAL you used was 46 grams in 17 DAYS, or about 2.7 grams per day. This is the “DAILY RATE”.

Finally, multiply the DAILY RATE by the number of days you need to provision and you get the total amount you’ll need. A 30-day supply would be 81 grams in this example. Just find the smallest, lightest container that will hold that amount, and you’re good to go, with what should be enough, but no extra.