Bath bomb boxes are one of the few packaging jobs where the maths does most of the work. The product is close to a sphere or a puck, the pack counts are predictable, and once you know your own finished diameter you can derive every footprint you will ever need without a size chart.
Start with a finished, wrapped unit
Do not measure the mould and do not measure a bomb straight out of the press. Measure one that has cured and been wrapped exactly as it will sell. Press moulds sold to makers commonly sit in the region of 2 to 2.75 in across, which is a useful industry reference point, but hand pressed bombs spread, edges flake and a shrink wrap or cello twist adds its own small amount. The finished, wrapped diameter is the number the die needs.
The pack arithmetic
Call your wrapped diameter d and pick a clearance. About 1/8 in per side is a normal working allowance for something that does not need to rattle, which means adding about 1/4 in to each axis in total. The example column below uses a 2.5 in bomb to show the shape of the answer. It is an example of the arithmetic, not a size we hold.
| Pack | Internal footprint | Worked example at 2.5 in |
|---|---|---|
| Single | d plus clearance, square | About 2.75 x 2.75 in |
| Two, in a row | 2d plus clearance by d plus clearance | About 5.25 x 2.75 in |
| Three, in a row | 3d plus clearance by d plus clearance | About 7.75 x 2.75 in |
| Four, two by two | 2d plus clearance, square | About 5.25 x 5.25 in |
| Six, three by two | 3d plus clearance by 2d plus clearance | About 7.75 x 5.25 in |
Depth is simpler. A single layer box needs the height of the bomb plus a little, and a bomb that is a true sphere needs its full diameter, which is why round bombs make deeper boxes than pucks of the same footprint. If you stack two layers, add a divider pad to the depth, not just the second bomb.
Dividers, crumbs and windows
Bath bombs shed. A multipack with no divider arrives as three bombs and a layer of dust, so a die cut fence or a moulded tray earns its place on anything above a single. Fences are cheap in corrugated and pulp trays hold round shapes better. What a box insert is covers which of those suits a fragile round product.
Windows are a common ask because the product is the marketing. A window costs a cut and a film, weakens the panel it sits in, and needs a wider margin than people expect around the aperture. If the bombs are unwrapped, a window also lets scent out and moisture in. Wrapped units behind a window are the safer combination.
Minimum, price and lead time
The minimum is 100 boxes, priced from about $0.48 per unit at bulk volumes and confirmed on your written quote. Since the die, the plates, design support, US shipping and a digital proof are included, a cavity cut to your own mould diameter costs no more to tool than rounding to someone else's size. Production is quoted per product in three lanes, rush (expedited production plus air freight), standard (air) and cost saver (sea), from about 7 business days, plus 2 to 5 for delivery. Two plants run the work, West Chicago and Guangzhou.
Measure one wrapped bomb, decide your pack counts, and send both numbers with your quote request so the dieline can be drawn to your product rather than to an average. If you are ready to order, custom bath bomb boxes is the product page.
