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Why fold panels are not all the same width
A folded leaflet looks simple when it is closed, but its panels are rarely equal. When one panel folds inside another, the inner panel must be slightly shorter or the fold buckles and the leaflet will not lie flat. This is the classic roll fold problem: a three-panel leaflet folded like a letter has an outer panel, a middle panel and an inner panel, and the inner panel is the one that needs shortening. The amount depends on the paper thickness, because thicker paper takes up more room in the fold. A thin 80 GSM sheet needs only a small adjustment, while a heavy 300 GSM card needs a visibly shorter inner panel.
This calculator works out panel widths from the flat sheet width, the fold type and the paper thickness. Choose a roll fold, a Z fold, an accordion fold or a gate fold, and the tool lists every panel in order with its width. The total is shown too, so you can check that the panels add up to the sheet you will print on.
How to use the calculator
- Enter the flat sheet width, the width of the paper before folding.
- Choose the fold type that matches your leaflet.
- Enter the paper thickness. If you only know the GSM, the paper thickness calculator on this site estimates it from weight and density.
- Read the panel widths from first to last and set your design guides to those widths.
A worked example
Take an A4 sheet, 297 millimetres wide, roll-folded into three panels on 0.1 millimetre paper. Dividing 297 by 3 gives 99 millimetres per panel, but the roll fold shortens the inner panel by twice the paper thickness, so the panels are 99, 99 and 98.8 millimetres. That 0.2 millimetre difference sounds tiny, yet it is what lets the leaflet close without a bulge. On thicker card the effect grows: with 0.4 millimetre card the inner panel becomes 98.2 millimetres, and ignoring that gap produces a leaflet that springs open.
Compare that with a Z fold of the same sheet, where every panel folds in a zigzag and no panel sits inside another. All three panels stay at 99 millimetres, and the leaflet lies flat without adjustment. A gate fold is different again: two outer flaps fold inward to meet in the middle, so the flaps are slightly shorter and the centre panels slightly wider. The calculator handles all three cases, so you do not need to remember which fold needs which adjustment.
Fold types at a glance
- Roll fold: panels wrap inside each other. The last panel is shorter. Good for letters and menus.
- Z fold: panels zigzag back and forth. All panels equal. Good for maps and step-by-step guides.
- Accordion fold: four or more panels zigzag. All panels equal. Good for long timelines and price lists.
- Gate fold: two flaps meet in the middle like doors. Flaps shorter, centre wider. Good for invitations and premium brochures.
Design tips for folded leaflets
Keep text away from fold lines by a few millimetres, because a fold line through a word makes it hard to read and can crack heavy card. Score thick card before folding, which means pressing a crease line into it with a scoring machine or a bone folder, so the fold lands exactly on the panel boundary. Always print a dummy on the real stock: fold it by hand, check that the inner panel tucks in cleanly, and confirm the leaflet closes flat. A dummy takes five minutes and catches panel errors that look fine on screen but fail in the hand. When the dummy closes flat and the panels line up, the design is ready for print.
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