Soap box sizes for common UK bars
Boxes here are made to the bar, not pulled off a shelf. Find your bar on the chart, check the inside size, and send us your millimetres if yours sits between two rows.
Which box size matches your bar?
Each row shows a common UK bar in millimetres and grams, with the inside box size worked out as the bar plus about 2 mm each way. Round shampoo bars and bath bombs are listed by diameter.
| Bar | Bar size | Weight | Box to fit, inside |
|---|---|---|---|
| Guest or hotel bar | 70 x 50 x 20 mm | about 50 g | 72 x 52 x 22 mm |
| Guest bar | 75 x 50 x 25 mm | about 60 g | 77 x 52 x 27 mm |
| Shampoo bar, round | 65 mm across x 25 mm | about 70 g | 68 x 68 x 28 mm |
| Small loaf-cut bar | 80 x 55 x 25 mm | about 80 g | 82 x 57 x 27 mm |
| Standard loaf-cut bar | 90 x 60 x 25 mm | about 100 g | 92 x 62 x 27 mm |
| Deep cut bar | 85 x 60 x 30 mm | about 110 g | 87 x 62 x 32 mm |
| Thick standard bar | 90 x 60 x 30 mm | about 120 g | 92 x 62 x 32 mm |
| Large bath bar | 100 x 65 x 30 mm | about 150 g | 102 x 67 x 32 mm |
| Bath bomb, round | 65 mm across | about 150 g | 70 x 70 x 70 mm |
| Three-bar gift set | 3 bars of 90 x 60 x 25 mm | about 300 g | tray of 200 x 95 x 30 mm |
How do you measure a bar with calipers?
Digital calipers are best, though a steel rule will do. Measure length, width and height at three points along the bar. Cut bars are rarely identical, so write down the largest reading for each side, in millimetres.
Weigh the bar as well. Grams help us sanity-check the size, but the box is built around the millimetres. Send both with your enquiry and we will confirm the inside size when we email your quote within one working day.
- Length: the longest edge, end to end
- Width: across the face at its widest point
- Height: the thickness, taken on the flattest part
- Weight: in grams, rounded to the nearest 5
Allowing for curing shrink and bevels
A cold process bar keeps losing water for weeks after the loaf cutter, so it shrinks a little. Measure at the point you will actually box it. If you pack at four weeks, measure at four weeks. Boxing a bar that is still sweating can mark the card, so let it cure first.
Bevelled edges take a little off the corners but leave the faces alone, so the box still follows your largest readings. Ash on a cold process top or a rustic hand-cut edge can add a millimetre, which means the roughest bar in the batch is the one to measure. About 1 mm a side is snug. Much more and the bar rattles in the post. Our page on box sizes by bar weight goes further into how weight and shape relate.
Sizing sleeves, bands and gift set trays
A sleeve wraps around the bar, so it is sized from the bar's width and height plus a small overlap. For a 90 x 60 x 25 mm bar, the loop around the long sides is roughly 170 mm before the overlap. Bands follow the same logic, and you choose how wide they sit along the bar.
Gift sets need a little more thought. Add up the bars, leave a gap between each, and tell us the layout you want, such as two bars side by side with a bath bomb above. The tray is cut to that plan. If you are building sets for hotels or favours, see our soap gift boxes for sets.
Questions
More answers in Help, or call +44 7578 382054 or message us on WhatsApp.
Why does a snug fit matter for posted soap?
Each dimension gets 2 mm of spare room, so roughly 1 mm of play on every side. For a 90 x 60 x 25 mm bar that means an inside of about 92 x 62 x 27 mm, enough to slide the bar in without letting it knock about and scuff its corners in a parcel.
What size box fits a 100 g bar?
Many 100 g bars measure 90 x 60 x 25 mm, which gives an inside box size of about 92 x 62 x 27 mm. Moulds differ, so measure your own bar before you order.
My guest bars are 75 x 50 x 25 mm. What is the inside size?
About 77 x 52 x 27 mm. Bars of around 60 g are popular with hotels and B&Bs, and the box can be printed with your room or property name.
How do I size a box for a round shampoo bar?
Measure across the widest point and the height. A 65 mm bar needs an inside of about 67 mm across, with the height allowance added on top.
Do bath bombs follow the same rule?
Yes. A 65 mm round bath bomb takes an inside of about 67 mm. Measure the widest point once the bomb is fully dry.
Should I measure bars before or after curing?
After, or as near to boxing day as you can manage. Bars shrink while they cure, and a box made to a fresh bar can end up loose.
What if my loaf cutter gives uneven bars?
Measure several bars and send us the largest readings along with the range. We make one box size per job, so it needs to suit the biggest bar in the batch.
How do I size a sleeve?
Send the bar size and tell us how much of the bar you want showing at each end. Our soap sleeves range is cut to the bar in the same way as boxes.
Can you make a size that is not on the chart?
Yes. Every box is made to the bar, so the chart is only a guide. Email your millimetres and we will quote by email within one working day.
Do I need to post a sample bar?
No. Measurements are enough for the quote. The free design proof shows the flat layout with your inside size, so you can check it against a real bar before anything is printed.
Tell us about your soap
Send the bar size in mm, a rough quantity and your logo or artwork. We reply by email within one working day with a price and a free design proof. Prefer to talk? Call +44 7578 382054 or message us on WhatsApp.