What is the Cardboard Sheet Calculator?
A regular slotted carton (RSC) is cut from a single flat blank. The cardboard sheet calculator works out the blank length (four panels plus a glue flap) and width (height plus two flaps), then calculates how many blanks fit on a sheet and the waste.
This helps box makers and buyers quote accurately. To draw a printable template of the blank use the Box Dieline Generator; for board weight use the Box Weight Calculator. All calculators accept centimetres, inches or millimetres and kilograms or pounds, so you can use the units on your supplier's spec sheet.
How to use the Cardboard Sheet Calculator
- Enter the inside box dimensions.
- Enter the glue flap width and board thickness.
- Enter the sheet size.
- Read the blank size, blanks per sheet and waste.
Formula
Blank length = 2L + 2W + glue flap · Blank width = H + W (two half-width flaps)
Example
A 30 × 20 × 15 cm RSC with a 3.5 cm glue flap needs a blank of about 103.5 × 35 cm. Two fit across a 110 × 72 cm sheet with about 9% waste.
Allowances in practice
Box makers add small allowances for board thickness at each fold (roughly the caliper per score) so the inside dimensions are correct. Use the thickness field to include them.
Related packaging and shipping tools
Packaging decisions are connected: the box size sets the volumetric weight, which sets the courier bill, and the carton size decides how many fit on a pallet or in a container. These related calculators help with the next step:
- Box size calculator: inside and outside box dimensions.
- Box volume calculator: volume in cm³, litres, CBM and ft³.
- Box weight calculator: empty carton weight from GSM.
- Corrugated box calculator: GSM and BCT strength.
- Box dieline generator: printable cut-and-fold template.
Frequently asked questions
What is an RSC box?
A regular slotted carton, the most common shipping box, where all flaps are the same length.
How is blank size calculated?
Length = 2L + 2W + glue flap; width = H + W.
What is a glue flap?
The joint flap where the box is glued or stitched, usually 3–4 cm.
Can it rotate blanks on the sheet?
Yes, it checks both orientations.
What is sheet yield?
The number of blanks you get from one sheet.
Is the Cardboard Sheet Calculator free to use?
Yes. The Cardboard Sheet Calculator on Custom Converter is completely free, with no sign-up, no daily limit and no watermark.
Does the Cardboard Sheet Calculator work on mobile phones?
Yes. It is built mobile-first and works on Android phones, iPhones, tablets and computers in any modern browser, with no app to install.