How to Choose the Right Size for Your Mailer Box

Can’t decide on the dimensions of your mailer boxes? Don’t worry. Here’s how to choose the right size for your mailer box.

Mailer boxes are a crucial component of any e-commerce brand.

Mailer boxes are cost-effective, easily customizable, and available in a wide range of shapes and sizes. High-quality mailer packaging also protects your products during shipping to ensure that they arrive damage-free at your customers’ doorsteps. Perhaps the most significant advantage of mailer boxes is that they can offer your customers a unique and memorable experience.

There’s no denying that mailer packaging can provide your brand with a ton of benefits. As such, choosing the right size for your mailer boxes is paramount. Can’t decide on the dimensions of your mailer boxes? Don’t worry. Here’s how to choose the right size for your mailer box.

1. Measure the dimensions of your product.

To determine what size you need for your mailer box, you need to measure the dimensions of your product first. Measure the length, width, and height of your product. The bigger your product, the larger the mailer box will be.

The rule of thumb for mailer boxes is that the size should just be big enough for the product to fit and be secure inside the box. Your product should be snug inside the box, so using an oversized mailer box is not a good idea.

custom mailer box dimensions

By using a mailer box that’s sized appropriately relative to the size of your product, you:

  • Prevent your product from moving around inside the packaging
  • Prevent damage to your product
  • Avoid using too much void fill or eliminating its use entirely

If your product has an irregular or asymmetrical shape, consider using a packaging insert with a cutout in the shape of your product to hold your product in place inside the box. For example, if you sell wine, you can use an insert shaped like the wine bottle so that the bottle is nice and secure.

2. Consider the different size ranges for your mailer box.

Do you need a small, medium, or large mailer box? Maybe you need a flat mailer box. Each of these options has a specific use, and which one is right for you will, again,

depend on the type of product you’re going to place in the box.


Think about a small cube, and that’s what the size of a small mailer box would be. Here at PackM, we can provide you with mailer boxes as small as 3 in x 3 in x 1.01 in (L x W x H).

Small mailer boxes are ideal for lightweight items such as jewelry, accessories, candles, and similarly sized items.


A medium mailer box can be similar to the size of a shoebox. Medium mailer boxes are a safe choice because they are versatile. You can put a wide range of products into a medium-sized mailer box, such as clothes, bags, small appliances, and even shoes!

medium mailer box


Large mailer boxes are big enough to fit hefty kitchen appliances like microwave ovens or high-end electronics such as televisions.


If your brand ships flat items that aren’t bulky like shirts, blouses, or even food items such as teabags, then flat mailer boxes are a perfect choice.

mailer box for flat products

3. Determine whether or not you need to use void fill.

Void fill is anything you put inside the packaging to cushion the product and prevent it from breaking. Examples of void fill include bubble wrap, packing peanuts, tissue paper, and kraft paper.

Your need for void fill depends on the type of product you are placing in the mailer box. Whether or not you need void fill will affect the size of your mailer box. If you need to use void fill, your box must have the space for it. In this case, you need a bigger mailer box.

For non-fragile products like food in a bag (chips, sweets, coffee beans, etc.), you can place them snug in a mailer box without a space for void fill because you don’t need to worry about the product getting damaged in transit.

On the other hand, void fill is absolutely necessary for fragile or breakable items like glassware, ceramics, or jars of food. You’ll need to account for adequate space in your mailer box to place the void fill.

4. Use internal dimensions when measuring box size.

After measuring the dimensions of your product and accounting for void fill, you can start looking for a company that can design and create high-quality mailer boxes for you.

When looking online for possible suppliers, you’ll notice the wide range of available sizes that companies have for their mailer boxes. Keep in mind that the measurements you see on the websites of packaging suppliers are the internal measurements of the boxes. Using the internal dimensions of the box ensures that your product will fit inside the packaging.

mailer box dimensions

You should never use the external dimensions of a box when measuring the size of your mailer boxes. Only use external dimensions if you want to either calculate the shipping costs of your product or determine how many of your mailer boxes can fit on a pallet.


If you need custom mailer boxes, we can help you. At PackM, we can provide you with durable, sustainable, well-designed, and easily customizable mailer packaging. We can even assist you in creating your custom design. Head to our website or call us at (424) 271- 0700. Our experts will be more than happy to help you create the perfect packaging for your small business.

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