How to make a cardboard box bigger?

Got an item that just won't fit? It's frustrating when your box is almost perfect. I'll show you how to easily make your cardboard box bigger.

To make a cardboard box bigger, you can use the "frankenbox" method. This involves combining two or more boxes. Cut one box open, slide it over another, and securely tape them together. This creates a larger, custom-sized container for your oversized item.

It sounds simple, but getting it right is key. A good join ensures your package is secure and looks professional. I've seen many people try and create a weak, sloppy box. It's better to understand the right methods. Let's break down the different ways you can adjust a box's size, starting with the most common adjustments we make in my business.

How to change carton box size?

Need to adjust a box for a better fit? Using an oversized box wastes materials and money. I'll show you how to easily change a carton box's size.

The easiest way to change a carton box's size is by re-scoring¹ it to make it shorter. Use a box resizer tool² or a utility knife³ to create new fold lines⁴. This creates a perfect custom fit for shorter items and saves on shipping costs.

Changing a box's size is a core skill in my line of work at Giftspack. It saves a lot of money and avoids ordering custom boxes⁵ for small runs. It’s a very practical skill.

Downsizing a Box with Scoring

This is the most common adjustment we make. It's perfect when your box is the right length and width, but too tall. First, place your item inside. Measure the extra height you need to remove. Then, using a ruler and a utility knife³, make shallow cuts, or scores, around the inside of the box at your wanted height. Don't cut all the way through the cardboard. You just want to create a new crease. After you score all four sides, use your knife to cut straight down each of the four corners to your new score line. Now you can easily fold the flaps down. Tape your perfectly resized box shut.

Upsizing by Combining Boxes

Making a box bigger is a bit more involved. We call it "frankenbox⁶ing" in the industry. It's great for one-off shipments of awkward items. Find two boxes of the same width and depth. Cut the bottom flaps off one box. Then, slide the open end of that box over the open end of the second box. You can adjust the overlap to get the exact height you need. Make sure you tape the seam where the two boxes meet very securely. I always recommend using multiple layers of strong packing tape⁷ for the best results.

How to change cardboard size?

Need to cut a large cardboard sheet down to size? One wrong cut can ruin the whole piece and waste material. I'll show you the right way to change its size.

To change the size of a cardboard sheet, use a sharp utility knife³ and a straight edge like a metal ruler. For best results, score the cut line first with light pressure. Then, make several more passes with increasing pressure to ensure a clean, straight edge.

As a packaging designer for over 16 years, I’ve cut my share of cardboard sheets⁸. Getting a clean cut is the foundation for any custom box. A jagged edge looks unprofessional and can even weaken the final structure. So, taking a moment to do it right is worth the effort.

Choosing the Right Tools

The right tools make all the difference. Always use a utility knife³ with a fresh, sharp blade. A dull blade will tear the cardboard, not cut it. I suggest using a new blade for every important project. You also need a heavy metal ruler or a T-square⁹. Plastic rulers can be cut by the knife, ruining your straight line. And finally, work on a proper surface. A self-healing cutting mat¹⁰ is best. It protects your table and keeps your blade from dulling too quickly. If you don't have one, a thick piece of scrap cardboard will work.

The Professional Cutting Technique

Here is the simple rule: measure twice, cut once. It's old advice, but it's true. Once you have your measurements, press your metal ruler down firmly along the cut line. Don't try to cut through the cardboard in one pass. Instead, do this:

1. First pass: Use light pressure to score the top paper layer. This creates a guide for your blade.
2. Second pass: Apply more pressure to cut through the corrugated flutes in the middle.
3. Third pass: Cut through the bottom paper layer to complete the cut.
   This multi-pass technique gives you complete control and a perfectly straight, clean edge every time. And always remember to cut away from your body.

How to adjust box size?

Your item fits the height of the box but not the width? It's a common problem. Let me show you how to adjust any dimension of your box for a perfect fit.

To adjust a box's length or width, you will need two identical boxes. Cut one side off each box, and then "sleeve" them together. The overlapping sections can be slid to get the dimension you need, then secured with strong packing tape⁷ for a stable new size.

Sometimes, just cutting a box's height down isn't enough. You might have a product that is long, like a lamp, or wide, like a piece of art. In these situations, knowing how to change the length or width of a box is a game-changer. It saves you from that desperate search for a perfectly sized box that might not even exist. The key is to see your two boxes as building blocks. With a little cutting and taping, you can reconfigure them to solve almost any packaging puzzle. Here are the main methods I use.

Which Method for Which Shape?

The best way to adjust a box depends entirely on the shape of your item. Trying to fit a long item into a box made wider will just lead to frustration. I tell my team to think about the item first. Here’s a simple table to help you decide.

Item Shape	Best Adjustment Method	Why it Works
Short & bulky	Downsizing (Scoring)	Reduces height for a snug fit and saves on filler.
Long & thin	Telescoping Method	Extends the length safely and securely.
Wide & flat	Side-Panel Method	Increases the width or depth for flat items.

The telescoping method¹¹ is great for things like posters or fishing rods. You just slide one box into another to make it longer. The side-panel method¹² is a bit more work but perfect for picture frames or computer monitors. You basically combine two boxes side-by-side to make one wider box.

How to make a big box using cardboard?

Need a truly giant box for a special item? A custom one-off order costs a fortune. I'll walk you through building a big box from simple cardboard sheets⁸.

To make a big box from cardboard sheets⁸, you will need several large pieces. Create six panels: a base, a top, and four sides. Score fold lines⁴, then join the panels using high-strength packing tape⁷ on all seams for a strong, custom-sized box.

Over the years, I've had to create custom boxes⁵ for everything from large machine parts to art installations. Building your own box from scratch seems daunting, but it's just about being methodical. If you can measure and cut straight, you can build a box of any size. It’s empowering to know you aren’t limited by standard box sizes.

Planning and Measuring Your Big Box

The most critical step happens before you even pick up a knife. First, measure your item's length, width, and height. Add at least one inch (or 2-3 cm) to each dimension. This gives you a little wiggle room. Now, plan your six panels on paper. You will need:

• 2 panels for the top and bottom (Length x Width)
• 2 panels for the long sides (Length x Height)
• 2 panels for the short sides (Width x Height)

Double-check your math before cutting. This simple planning stage prevents costly mistakes and wasted cardboard.

Assembling and Reinforcing

Once your six panels are cut, it’s time to build. Lay your bottom panel on the floor. Arrange the four side panels around it. Use strong packing tape⁷ to join the sides to the base, creating tape "hinges." Tape both the inside and outside seams for extra strength. Next, lift the sides up and tape the four vertical corners together, again taping inside and out. Your box will now hold its shape. For heavy items, you can add extra support. Cut cardboard triangles¹³ and glue them into the corners for rigidity. Or, you can create a double-walled box¹⁴ by lining the inside with another layer of cardboard. Once your item is inside, place the top panel on and tape it securely.

Conclusion

Making a cardboard box bigger is simple. Whether you combine existing boxes or build from scratch, you can create the perfect size for any item with these practical techniques.

---