Determine the number of people you'll need to feed.
Estimate the number of calories that each person requires per day using a handy online calculator (http://www.mayoclinic.com/health/calorie-calculator/NU00598).
Factor in any physical activity (http://www.wellsource.org/mhc_home/hcfit/activity_calc.htm) and exposure to cold temperatures. These will make your caloric requirements increase. According to Nancy Clark, MS, RD, a nutrition counselor, if you get cold enough and start to shiver, you can burn up to 400 calories an hour. (See Reference 1.)
Determine the approximate total number of food calories you'll need per day by adding all of the individual requirements together.
Estimate how long you will need food supplies to last.
Multiply the daily caloric requirement number by the number of days to get an approximate number of calories your group will need to survive.
Understand that in most survival situations you do not know when help will arrive, so prepare for the worst-case scenario.
Get the most from your calories. Invest in foods with a long shelf life and maximum nutrients.
Explore your food options: emergency rations such as Mainstay and ER bars are specially formulated as high-calorie, long-lasting, nutrient-efficient survival food for people stranded outside the home. Freeze-dried and dehydrated meal kits are another option that provide variation and nutrition. (See Reference 2.)
Stock up on pantry goods (six-month shelf life, sealed) and foods in cans and jars (up to one year, unopened) for home survival in emergency situations.
Calculate the amount of food you would need for a year for your family: (http://www.areyouprepared.com/Food-Storage-Calculator-s/109.htm).
