Which size fits your needs? With so many poly bags in different sizes and shapes, it is easy to get confused. And yet, the right poly bag size means your products are protected, easy to seal, and well presented.
If you are finding it hard to match the poly bag to your line of products, we have put together a guide that explains how to measure for layflat, gusseted, reclosable, and poly tubing bags.
Why Measuring Matters
Picture your poly bag as a cloth: you want it to fit nicely the product it will contain, otherwise it could be too tight or sagging.
A poly bag that’s too tight can tear, while one that’s too big wastes material and space. From our experience, customers who follow measurement formulas avoid 90% of sizing issues and reduce returns or damaged goods. The right-sized bag increases your business efficiency and your overall turnover.
Packaging Friends offers all standard poly bag types, including layflat, gusseted, reclosable, and poly tubing, with reliable, industry-consistent sizing. Our measurement guidelines are built on years of practical experience to help customers select the right fit the first time, every time.
Quick Reference Chart: Bag Type Width Formula Length Formula Example
Layflat W + D + 2" H + D + 6" 14×10×32 →
26×48 Gusseted W + 1" / D + 1" H + D + 6" 18×12×14 →
19×13×32 Reclosable W + 1½" L + 1" 2½×5 →
4×6 Poly Tubing (Diameter × 3.14) ÷ 2 + 1–4" Variable 12” D →
20” width
Layflat Bags (Square Containers or Dimensional Products)
Layflat bags are used for flat or rectangular items such as boxes or stacked materials.
When you measure your item, depth refers to the shortest dimension (typically the front-to-back thickness of a box or product). It’s often less obvious than width or height, but it is important to get the right fit.
Also, remember that extra inches give enough space to close the bag. The additional inches in the formula aren’t just padding. They provide space to close the bag, which includes sealing, tying, or folding it. A bag that’s bulging or too tight could tear or stretch too much when packaging your items, and you don’t want that.
These sizing guidelines apply to any product with a flat or boxy shape, for example, books, electronics, apparel stacks, or cartons. Our layflat bag formula below is easy to follow and a reliable fit.
Formulas
1. Bag Width = Container Width + Container Depth + 2" (for a looser fit)
2. Bag Length = Container Height + Container Depth + 6" (to cover contents and allow tying)
Examples
● Container: 14” W × 10” D × 32” L → Bag: 26” W × 48” L
● Object: 10” W × 3” D × 16” L → Bag: 15” W × 25” L
Gusseted Bags (Square Containers or Dimensional Products)
Gusseted bags are used for products that need side expansion, such as boxes or irregularly shaped containers. Side gussets add volume and extra flexibility, as they have expandable side panels that open up as the bag is filled. This added feature increases internal space and lets them accommodate wider or more irregularly shaped items more easily than flat bags.
Their flexibility makes them ideal for bulkier items, as they can accommodate them without stretching or distorting the plastic. The bag keeps its initial shape, doesn’t puncture or tear. This type of poly bag is thus ideal for packaging boxes, containers, or grouped parts that need extra room.
Formulas
1. Bag Width = Box Width + 1"
2. Bag Depth = Box Depth + 1"
3. Bag Length = Box Height + Box Depth + 6" (to cover contents and allow closure)
Examples
● Box: 18” W × 12” D × 14” H → Bag: 19” W × 13” D × 32” L
Reclosable Bags
Reclosable bags are used for resealable storage or display packaging.
Unlike layflat or gusseted bags, reclosable bags are measured from the bottom seal to just below the zipper, rather than the top edge, because you can’t use the space between the zipper and the top. These measurements give the right usable interior space, calculated accurately for product fit and sealing.
Custom reclosable bags from Packaging Friends feature reinforced hammer seals for added durability. This makes them especially reliable for heavier or high-use applications.
We have put together a helpful guide regarding the differences in appearance between domestic and imported bags. The look and packing style of poly bags depend on where they are made. If you want to learn more about these differences and choose what’s right for your use, check our guide: Poly Bag Appearance and Packaging: What You Need to Know.
Formulas
1. Bag Width = Product Width + 1½"
2. Add ½" more for rigid or hard items.
3. Bag Length = Product Length + 1"
4. For thicker or bulky items, add the product’s depth to both Width and Length. 5. Add ½" to 2" for a looser fit.
Examples
● Flat Product: 2½” W × 5” H → Bag: at least 4” W × 6” L
Poly Tubing
Poly tubing is used for packaging long or irregularly shaped items where the length can vary.
These bags are ideal for variable-length products or custom bag sizing. Poly tubing is a flexible solution for items with variable lengths or for creating multiple bag sizes from a single roll. It’s commonly used in manufacturing and shipping operations that need to be efficient and adaptable.
If you are ordering poly tubing, keep in mind that dimensions are measured flat, not by diameter. Specifically, the listed width refers to the flat, uninflated measurement across the tubing and does not include the tubing's diameter. To fit round items, you’ll need to use a simple formula that converts diameter into flat width.
Formulas
Flat Width = (Product Diameter × 3.14) ÷ 2 + Adjustment
Adjustment: add 1" for a snug fit, or up to 4" for a looser fit.
Examples
● Round Product: 12” Diameter 12 × 3.14 = 37.68 ÷ 2 = 18.84 + 1" = 20” tubing width
How to Order the Right Size
If you want to avoid returns and mismatches between products and bags, our measurement guides above include the formulas you need to calculate the size of the poly bags you need.
The right bag sizing protects your products better and gives a cleaner and more professional look, not to mention how you waste less material over time (which means you save more money).
We have a wide selection of poly bags. You can order standard sizes, or we can work together to create custom bags for specific products. If you are unsure about what you need, the team at Packaging Friends is always available to help. Reach out to us if you need support with bag sizes, are looking for bulk orders, or are interested in specialty applications. We’ll make sure you get exactly what you need. Orders over $1,000 qualify for free shipping with bulk discounts.
If you’d like to learn why small size differences occur during production, visit .Understanding Width, Length, and Gauge Tolerances for Plastic Bags. And if you want to understand how bag thickness affects strength and flexibility, check our guide Understanding “Mil” Thickness in Plastic Products.