What is a gusset.
A gusset is the fold that gives a bag its depth. This page explains the two kinds, how to read one in a bag size, and how deep it needs to be for what you pack.
The short answerA gusset is the folded panel in the side or base of a bag. It opens out as the bag fills, so a flat bag becomes a box with depth. In a bag size it is the third number: 26 × 32 × 12 cm means 12 cm deep.
Side gusset and bottom gusset
A side gusset is a fold down each side of the bag. Paper carrier bags, block bottom bags and many coffee bags have them. The sides fold in while the bag lies flat and open out as it is filled.
A bottom gusset is a fold in the base instead. It is what makes a stand-up pouch stand: the fold opens into an oval floor under the weight of the contents.
Side gusset
Folds down each side that open out as the bag fills.
Bottom gusset
A fold in the base that opens into a floor, so the pouch stands.
How to read the gusset in a bag size
Paper and fabric bags are written width × height × gusset. Width runs across the face, height from top to bottom, and the gusset is the depth of the base when the bag is open. The height does not include the gusset.
Pouches are written width × height + gusset, because the gusset sits in the base. Our 250g pouch is 13 × 20 cm with a 7 cm bottom gusset. Thermal delivery bags are boxes, so they read width × depth × height instead.
What the gusset changes
- Capacity. Multiply width × height × gusset and divide by 1,000 for litres. A 26 × 32 × 12 cm bag holds about 10 litres filled to the brim.
- Standing. A bag with a gusset stands open on the counter while you fill it. A flat bag does not.
- What fits. A box sits on the base of the bag, so the gusset has to be at least as deep as the box.
How deep should the gusset be?
Measure the deepest thing that goes in, lying the way it will travel, and add a centimetre or two. Meal boxes, cake boxes and shoe boxes set the gusset; flat items such as documents or folded garments need little depth.
Bags without a gusset exist too. A flat cotton tote of 38 × 42 cm or a flat greaseproof bag suits flat and soft goods, and uses less material. Every bag in the range can be cut with the gusset you need.
Questions
What does gusset mean on a bag?
The folded panel in the side or base that lets the bag open out and hold depth. On a size like 26 × 32 × 12 cm, the gusset is the 12.
Is the gusset included in the height?
No. Height is measured on the face, top to bottom. The gusset is a separate number for the depth.
What is the difference between a side gusset and a bottom gusset?
A side gusset folds down each side, as on paper carrier bags. A bottom gusset folds into the base, as on stand-up pouches, and it is what makes them stand.
Where does the word come from?
From tailoring, where a gusset is an extra panel sewn into a seam to add room. Bags borrowed the word for the same job.
Can I choose the gusset size?
Yes. Every bag is made to your size, gusset included, at the same minimum order and lead time as a standard size.
Written by the Bag Bureau production team. Last updated October 2026.