How to Measure a Tuck Box: Inside Sizes, Flaps and Clearance
Taking length, width and depth so the product slides in and the flaps still close.
By the Tuck Boxes carton desk · Updated
Why do carton makers ask for inside sizes?
A tuck box is drawn from the inside out. The dieline starts from the space your product needs, then adds board thickness, creases and flaps around it. If you send outside sizes, the box ends up smaller than you expect.
So every size we quote is an inside size in millimetres, written as length × width × height. Get those three numbers right and the rest of the carton follows from them.
Inside sizes also travel well between suppliers. Two printers can use slightly different board, so their outside sizes differ, but the space for your product stays the same.
Which side is length, width and height?
Look at the opening of the box, the end that the tuck flap closes. The longer side of that opening is the length. The shorter side is the width. The height is the distance between the two openings.
For a dropper bottle standing upright, the opening is the small square at the top. Length and width are both close to the bottle's diameter. Height is the tall side. For a flat card deck in a tuck top, the opening is the large face, so the height is the shallow one.
Writing the sizes in the wrong order is the most common reason a first proof needs a second look.
How much clearance should you add?
Clearance is the gap between the product and the inside of the carton. Too little and the product jams or the tuck bulges. Too much and it rattles. The figures below are common starting points, not fixed rules.
Clearance also depends on how the product goes in. A bottle slid in from an end needs a touch more room than a bar laid in from above. It has to pass the dust flaps on the way.
| Product type | Add to length and width | Add to height | Why |
|---|---|---|---|
| Rigid glass bottle or jar | 1.5 to 2 mm | 2 to 3 mm | Glass does not flex, so it needs room to slide |
| Soap bar or wrapped block | about 1 mm | 1 to 2 mm | A snug fit stops the bar shifting |
| Card deck | about 1 mm | about 1 mm | Cards should not slide loose inside |
| Pump or spray bottle | 1.5 to 2 mm | 3 mm above the nozzle | The head is taller than the body |
| Product in a rise-up insert | measure the insert | measure insert plus product | The insert sets the size, not the item |
When in doubt, send the product's exact size and say how it packs. Our designers add the clearance and show it on the proof.
Measuring a product step by step
A tape measure is fine for a rough figure, but it often reads a millimetre or two out on small items.
Measure on a flat table, with the product standing the way it will sit in the box. Hold the callipers square to the side, not at an angle, and read the figure to the nearest half millimetre.
- Use digital callipers if you have them, or a steel rule read in millimetres.
- Measure the widest point on each side, including caps, pumps, labels and shoulders.
- Measure two or three samples, as filled bottles and hand-poured jars can vary by a millimetre.
- Write the largest reading for each side.
- Decide which face is the opening, then label the numbers length, width and height.
- Add clearance from the table above, or leave it to us and say so.
- If the product has a sleeve, tissue or insert, measure with it in place.
How do flaps and board change the outside size?
Board adds to the outside of every wall. A 350gsm white board is commonly around 0.45 to 0.5 mm thick. Each side grows by roughly that much, plus a little for the crease. On a typical carton, the outside is about 1 to 2 mm larger than the inside on length and width.
Flaps are worked out from the inside size too. A tuck flap on a small carton is usually about 12 to 20 mm deep. A glue flap along the side seam is often 12 to 15 mm wide. Dust flaps are sized to the width of the end panel.
- Narrow ends under about 20 mm wide make small dust flaps, which are fiddly to fold.
- Very short tuck flaps can pop open. Most layouts keep the tuck at least as deep as it is practical to grip.
- Thicker board needs slightly wider creases, which adds a fraction to the outside size.
Our guide to board weights and thickness explains gsm and calliper in more detail.
How do you size a box for an awkward shape?
Tapered bottles, droppers with tall teats and jars with wide lids all have one point that sets the size. Measure that point, not the body. A dropper bottle often needs its height taken to the top of the teat, then 2 to 3 mm added.
For round items, the length and width are usually the same, taken across the diameter. Our custom dropper bottle boxes show how a square opening fits a round bottle.
Do inserts change the measurements?
Yes. Once an insert goes in, the carton is sized around the insert, not the product. A card insert with a cut-out adds its own board thickness on each side it touches. A rise-up insert adds height under the product.
Measure the product first, then tell us the insert type and we work out the carton size. The tuck boxes with rise-up inserts page shows how the platform lifts the item into view.
For a jar, the round cut-out in a card insert is usually 1 to 2 mm wider than the jar. Too tight and the jar is hard to lift out.
What about packing several cartons for posting?
If you post cartons inside a shipping box, the outside size matters too. Add the board and crease allowance to your inside size, then plan how many cartons sit in each layer.
Candle jars are a common case, since several cartons often travel together to a shop. Our printed candle tuck boxes page lists typical sizes for common jar diameters.
Say each carton is 80 mm square outside. Twelve of them, three by four, fit a shipper of about 245 × 325 mm inside. Leave a few millimetres for the shipper's own board.
What does a finished size brief look like?
A clear size brief fits on one line. It names the inside size, the opening and the closure. For example: inside 42 × 42 × 128 mm, opening at the top, reverse tuck end.
Add anything that changes the fit, such as an insert, a window or a hang tab. If the product is fragile or has a pump, say so too.
- Inside length × width × height in millimetres.
- Which end opens, or that it is a tuck top.
- The closure you want, or ask us to suggest one.
- Any insert, window or hang tab.
- Whether you have added clearance already.
With that line, our designers can draw the dieline and send a free proof without a back-and-forth.
Common measuring mistakes to avoid
- Sending outside sizes from an old box without saying so.
- Measuring the body of a bottle and forgetting the cap.
- Using a size from a supplier's listing instead of the product in your hand.
- Adding clearance twice: once yourself, then again when we add our own.
- Mixing up the opening face, so a tall box comes back short and wide.
Not sure of any number? Send what you have through the quote request form and say which figures you measured. You see the carton drawn to size on a free proof before anything is printed.
