Paranoid Prepper: How To Set Your Prepping Ammo Budget & Inventory

Some time back Salty wrote a post about the minimum amount of ammunition to have on hand.  This has also been a perennial favorite topic on various prepper forums.  There are also YouTube videos on the subject.  The figures tossed around are generally set numbers, without much thought to the individual prepper’s circumstances.  I’d like to suggest a method of determining an appropriate ammunition inventory that takes those circumstances into account, allowing each of us to figure out how much ammunition makes sense, given our individual circumstances.

Factors to Consider

Ammunition needs to be available for each of our firearms, which raises the question of what the firearms are used for.  Basically, as preppers, we are going to need ammunition for three activities:

  • Training
  • Self Defense
  • Hunting

We also need to consider how long the ammunition is expected to last.  If someone is prepared overall for a weeklong event, such as a hurricane or other natural disaster, not much ammunition is required.  On the other hand, if a prepper has stashed food for a year, or prepared for an EMP, firearms and ammunition should be on hand in significant quantities.  Most of us are somewhere in between.  We are adequately prepared for short term disasters, and working toward being prepared for longer term disasters.  Since ammunition can be acquired gradually, it makes sense that we build the inventory gradually, in balance with our other preps.

Finally, we need to consider the size of our group.  An individual will not need as much ammunition as a 50 person MAG.

Reducing these factors to an equation

Since the amount of ammunition required is going to be variable from prepper to prepper, we need a formula to determine how much each prepper needs.

If the training ammo required for a month is T, the Self Defense Ammo for a month is S and the Hunting ammo is H, then one month’s ammo for one person is:

I = T + S + H

We can extend this to include the number of months N, and the number of people P.

I = (T + S + H) * N * P

If you want to consider caliber, simply use this equation for each caliber.

Applying the formula

Let’s try this for a hypothetical MAG with 10 armed individuals, that is currently at a point of being prepped for 3 months.  The target may be longer, but 3 months is where they are at the present time.  How much ammo should this group have?

We will use 22LR for training and a bit of small game, but not for self-defense.  If we use 100 rounds for training, and 25 rounds for hunting, we get:

N = 3

P = 10

T = 100

S = 0

H = 25

Resulting in:

I(22LR) = (100 + 0 + 25) * 3 * 10, or 3750 rounds of 22LR.

You can vary any of the variables for your circumstances.  For instance, do you think you may be shooting lots of squirrels and 25 is too low for your group?  Just change H to a higher number.  Is your group really prepared not for just 3 months, but for 6 months?  Then change N to 6.

Want to try center fire rifle?  Let’s say we still have N = 3 and P= 10, but we aren’t going to train with this, we will use our center fire rifle ammo, hypothetically 5.56 for self-defense, so S = 30 and hunting  larger game, so H = 5.  What is our result?

I(5.56) = (0 + 30 + 5) * 3 * 10, or 1050 rounds of 5.56

Once you have worked out your formulas for each caliber your group needs, you may find you have more than you need in one caliber and not enough in another.  This can guide your purchases as you continue to stock.

Other Uses

If you want a sense of the cost of this inventory, just add a factor for cost C, or cents per round to translate rounds into a monetary amount:

I (in dollars and cents) = (T + S + H) * N * P * C/100

Let’s say instead of determining a desired inventory, you have an inventory and want to determine how many months it should last.  In this case we need to do a little algebra to determine:

N =               I / ((T + S + H) * P)


Given the volatile nature of ammo prices, you may want to get ahead of your other categories of preps when prices are low.  However, if you are behind on your ammo inventory vs. other preps, you really aren’t as prepared as you might think.  For instance, if you have 2 months of food, and 3 months of ammo, you are prepared for 2 months.  However, if you have 3 months of food, and 2 months of ammo, you are still only prepared for 2 months.

If you like this method, try putting the formula into a spreadsheet for each caliber.  Want to see how much you need to be prepared for another month?  Increase N by 1.  Want to see what happens if you add 2 people to your group?  Add 2 to P.

I hope this helps you with your prepping.


Paranoid Prepper


  1. I’ve never thought very much about how much ammo to keep, I just have kinda bought some and stuck it in a couple of boxes.

    I need to think about what I am doing a bit more.

  2. This is a pretty common topic in prepper circles. Since you are in the US, now is a good time to stock up. We don’t have any of the runs like we got after Sandy Hook going on, so availability is good.

  3. My biggest issue is space I have to keep my ammo locked up (the better half insists) so I am short of where I want to be and way short of where your formula puts my needs.

    • Depending on how secure you need to be, there are inexpensive locking cabinets from Stack On, and there are even locks for individual ammo cans. Locked doesn’t necessarily have to be an expensive safe, albeit a nice safe is, . . . nice. 🙂 Locked can even be a padlock on a closet.

      • I have a bunch of those cabinets, like a BUNCH of them… I’m much more concerned about my firearms being stolen than I am a fire (I have 3 different structures where my guns are stored, so worst case I would lose one of my 3 sets of guns). They work great, bolt em to the floor and to the wall, and they aren’t going ANYWHERE.

  4. Good article as usual. If things ever got really bad balancing target practice with playing the “grey man” would probably mean a lot less practice ammo needed after the 1st month or 2. But practice builds muscle memory and several people in our group need more practice so practice would probably continue for several months. It’s a balance between staying quiet and being proficient with a firearm.
    I keep a decent fire resistant gun safe in the house with some ammo for each weapon. But I also keep most of my ammo in a “job box” like you see on construction sites in a metal building. The ammo wouldn’t all fit in the gun safe and if the home ever caught fire I wouldn’t want ammo cooking off discouraging the firefighters. I also store my fuel outside in a “garden box” because I don’t want 30 gallons of gasoline in my garage.
    Still, I think some more 22 ammo would be worth getting.

    • If I understand you correctly, you think your needs would change with time. If so, factors T, S, and H would need to be functions, instead of set amounts. That would make the math a bit more complex, but is very much in the spirit of what I am suggesting with this post. I encourage you, and other readers, to alter the formulas to match your circumstances.

    • Perhaps using a range a little farther from home would solve the ‘gray man’ dilemma. So what if some folks who don’t know who you are or where to find you know that you’re shooting?

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