How to Choose the Right Mailing Bag Size

Mailing bags are one of the simplest and most cost-effective ways to send soft or non-fragile items. But choosing the wrong size is easy to do. A bag that's too tight can split or refuse to seal, and one that's too big looks untidy, lets items slide around and can push you into a more expensive postage band. Here's how to get it right.

1. Measure your item as it will be packed

Fold or prepare the item exactly as you'll send it, then measure:

• Width: the widest point side to side.
• Length: top to bottom.
• Depth: how thick it is when folded.

If you're adding a packing slip, tissue paper or a free gift, include those when you measure.

2. Allow for the depth

This is where most people go wrong. A flat bag has to wrap around the thickness of your item, which uses up some of its width and length. As a rough guide, add the depth of your item to both the width and the length, then allow a little extra room so the bag closes easily.

3. Remember the seal

Most mailing bags have a peel-and-seal adhesive flap. The size usually quoted is the usable space below the flap, but it's worth checking. Make sure there's enough room for the flap to fold over and stick flat without strain.

4. Think about your postage size limits

Postage is often priced by size and weight. Thin, flat parcels can sometimes travel in a cheaper band than bulky ones. Before choosing a standard bag size for your business, check your carrier's current size and weight limits and pick bags that keep your most common orders within the cheapest band that fits.

5. Pick a few standard sizes for your shop

If you sell online, you don't need dozens of sizes. Most sellers manage with three or four that cover their range, for example:

• Small: accessories, socks, phone cases, cables.
• Medium: T-shirts, leggings, small bundles.
• Large: hoodies, jumpers, bedding or multi-item orders.
• Extra large: coats or bulky soft goods.

Fewer sizes means simpler stock control and you can buy each one in bulk for a better price.

6. Choose the right thickness

Thicker bags are more tear-resistant and better at hiding what's inside, which is useful for higher-value items. Lighter bags are fine for everyday soft goods. If you're unsure, start with a mid-weight bag and adjust based on how your parcels arrive.

7. Know when a bag isn't the right choice

Mailing bags are best for soft, unbreakable items. For fragile, sharp-edged or rigid products, a padded envelope or a box will offer better protection.

Ready to stock up?

Buying your go-to sizes in bulk keeps the cost per parcel down. Browse our mailing bags or get in touch for bulk and trade pricing.