The Hard Math of Being Prepared

Take the Supplies You Think You Need and Multiply Them by This Number

How much emergency food and water do you really need?

That’s the first and most fundamental question of emergency prep, and we hate to say it but many of us get it wrong.

The reason why is simple: When we plan emergency food, many of us visualize a regular-sized family meal with mom and dad and maybe a kid or two.

But what we should be visualizing is a much more crowded table. 

people eating meals together

Nothing brings your entire tribe together like a disaster, and if you’re emergency planning for just the people in your household, chances are you’ll come up short when things hit the fan.

We call this the “hard math” of prep—knowing the true number of mouths you’ll be feeding in a disaster and planning accordingly.

Today we’ll talk about how to do that math (hint: it’s multiplication, not addition) and how to stock the amount you really need.

How to Do the Math

For every prep-minded person, there’s a magic number—the sum total of people you will realistically need to prep for.

That number varies widely from person to person. If you haven’t yet, we suggest that you sit down and calculate it right now. It’s going to be the guiding benchmark for all your preps. 

Here’s how to do it.


Not to overstate the obvious, but you are the common denominator in your own emergency preparedness. You need to take care of yourself first, or you’re no good to anyone else.

This math is easy. Most emergency kits and supplies you can buy are designed for one person. For example, Emergency Essentials’ 30-Day Emergency Food Kit will feed one person for 30 days, a three-month kit will feed one person for three months, and so on.

Magic Number: 1


couple canning food

For those with a husband, wife, boyfriend, girlfriend, or even a roommate…here’s the number-one person you need to calculate for after yourself. If you’re lucky enough to have them, this will be your partner in disaster.

Make sure they’re taken care of.

Doing the math we discussed above, you simply divide by two. Therefore, with two people, a 30-day kit will last 15 days, a three-month kit will last one-and-a-half months, etc. Easy enough.

Magic Number: 1 + 1 = 2


This is where the math starts to get a little more brutal. If you’ve got children or other dependents living with you, you’ve got to add them to the equation.

The average American family has 2.5 children. Let’s round that up to three to be safe. That means if you’re living with an average-sized family, you’ll need to divide any kit you purchase by five. Now that 30-day kit will last only six days, the three-month kit will last 18 days, and so forth.

Magic Number: 2 + 3 = 5


couple watching house torn down

If there’s one thing we’ve learned after talking to thousands of disaster survivors over the years, it’s that once the people in your home are safe and accounted for, your thoughts are going to turn immediately to family members that live nearby. These could be your kids, grandkids, parents, aunts, cousins, etc. If you’re like most of us, you won’t be able to sleep soundly till you know these special people are taken care of.

And if they’re not prepared (which, let’s be honest, many won’t be) you will want them by your side as soon as possible.

That means you’ll have to add them to your magic number. This is where people’s sum totals will really start to differ. However, as an average let’s say most of us have at least a couple family members nearby we’re invested in protecting.

Tracking with our previous calculations, a 30-day kit for your entire group will now last about four days, a three-month kit will last 12 days, and so on.

Magic Number: 5 + 2 = 7


Besides our families, most of us have people in our lives who know we’re prepared. They may tease us from time to time about the stacks of #10 cans in our closets…but you can darned well bet that at least a few of them will end up on your doorstep when disaster strikes. Again, the thousands of survivors we talk to report that this happens all the time during major emergencies. 

How do you plan for the people that come to you for help?

First, we should all establish boundaries—but this can be difficult in emergencies when people around you have nowhere else to turn.  Based on our experience, the safest thing to do is prepare for this ahead of time. List out in your mind those people who may come asking for assistance and plan on putting away a little something extra for them.

Note: this shouldn’t be your first priority, but it’s a prudent decision if you have the means.

As you calculate this figure, we recommend adding one more person to the total…for that unexpected visitor you never saw coming.

If you’re like most of us, the number of friends and neighbors you list out will probably be around five. If you’re the friendly type, it might be higher.

Your magic number just grew! (And the staying power of your emergency supply shrank along with it.) A 30-day kit will now last you a measly two-and-a-half days, a three-month kit will last seven-and-a-half days, etc.

Magic Number: 7 + 5 = 12  


30 days of food x 12 people = a one year food supply

Now that you’ve got your magic number calculated, the hard math begins! Decide on the amount of time you’re prepping for and multiply it by your magic number.

That’s roughly how much food you’re going to need in a worse case scenario.

So, to prepare to support twelve people for 30 days, you’re going to need about a year of food. Yikes!


There are a couple pieces of good news here.

First, not everyone in your “magic number” group is going to rely 100% on you. They’ll have some food in their cupboards. Heck, if you’re lucky they may even have emergency food. So that magic number is a high-ball, worse-case scenario total.

Second, you likely won’t be supporting everyone in your group for the entire duration of the disaster. Barring an all-out apocalypse, most people will find other ways to take care of themselves after the first few weeks.

To be safe, we recommend using your total magic number to calculate your needs for the first two weeks to 30 days. After that, reduce it to include only the people in your household.

Of course, if you have the means, there’s nothing wrong with preparing to support your group for months or even a year.  

How to Stock Up in Volume

buy 3 months of food and get 1 month of food free

Now that you’ve done the hard math and calculated how much emergency food you really need, here are a few tips for stocking up.

Find Sales Where You Get Extra for Your Money – If you’re an Emergency Essentials newsletter subscriber, you should be getting special deals every week. These offer big savings that add up to free food, water, and gear over the course of time. If you make a plan to consistently purchase during sales, you’ll gradually be able to put away the extra surplus you need for the people in your life.

This week, for example, we’re running a sale where if you buy a 3-Month Emergency Food Kit, you’ll get a 30-Day Emergency Food Kit free! We encourage you to check it out—it’s exactly these kinds of savings that will get you to your goals.

Focus on Community Preparedness – The truth is, many of the people in your group of close friends and family may not pitch in in significant ways when it comes to preparedness. 

But you may not need them to—not if you have enough support from neighbors and your community. 

Check out our guide to community preparedness to see how you can work side-by-side with the prep-minded folk around you to get the supplies you need (without bearing all the cost and burden yourself).

person planting seeds in the garden

Find Alternative Ways to Get Your People Involved in Prep – If friends and family are slow to get on board with preparedness, you may have some luck leveraging the activities they already love to help them get prepared.

Does your son like gardening? Ask him to grow crops your family needs for the emergency food supply. Does your spouse enjoy making jams and jellies? See if she’s open to expanding her canning repertoire to include other items for your food storage. Have a gear head in the family? Get them to help you store up more fuel. Emergency preparedness is such an expansive activity—there are an endless number of ways loved ones can pitch in.

Take Advantage of Wakeup Calls – We don’t want the disasters we’re preparing for to happen, but when they inevitably do, we can take advantage of them. After the earthquake or storm or wildfire has passed, your loved ones’ interest in emergency preparedness will likely be at an all-time high. Seize that moment to involve them in your passion for preparedness (and hurry, their interest may wane as time goes by).

Gamify Prep – For children especially, making a game out of preparedness can help get them ready for disaster whether they realize it or not.

For example, one earthquake survivor told us that when her children were young she used to play a game where she’d turn off the lights and see how quickly they could get out of the house in the dark. A little dangerous maybe, but they sure had fun doing it, and it absolutely got them prepared to evacuate during a disaster. 

You Can Do It!

Hopefully, talking realistically about the “hard math” of emergency preparedness doesn’t feel too daunting. The truth is, none of us are perfect, and anything extra you can put away to help protect the people you love is better than what they’d have on their own. Make a plan, give yourself plenty of time, and you’ll get where you want to be.

We’ve seen thousands of families reach their emergency preparedness goals, and you can too!

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