Quick answer: B3 is 353 × 500 mm, B4 is 250 × 353 mm, B5 is 176 × 250 mm, and B6 is 125 × 176 mm. Together they cover the middle of the ISO B series, from small posters to compact books.
Measurement note: dimensions are stated width × height in portrait orientation. Turn the sheet through 90 degrees for landscape use. Millimetres are the controlling values for ISO sizes; inch figures are rounded conversions.
Dimensions and typical uses
| Size | Dimensions | Inches | Typical uses |
|---|---|---|---|
| B3 | 353 × 500 mm | 13.90 × 19.69 in | posters, drawings and large book pages |
| B4 | 250 × 353 mm | 9.84 × 13.90 in | books, magazines, art and presentation sheets |
| B5 | 176 × 250 mm | 6.93 × 9.84 in | books, notebooks, journals and manuals |
| B6 | 125 × 176 mm | 4.92 × 6.93 in | small books, pocket notebooks and cards |
B3
B3 provides noticeably more space than A3 while remaining smaller than A2. It is useful for small posters, drawings, presentation sheets and publications that need generous pages. Because it is not a universal office-printer size, confirm equipment and stock before designing.
B4
B4 is well suited to books, magazines, catalogues and art reproductions that should feel substantial without reaching A3. ISO B4 is 250 × 353 mm. Be alert to JIS B4, which has different dimensions.
B5
ISO B5 at 176 × 250 mm is a comfortable book and notebook size. It gives more writing area than A5 but remains portable. Many notebooks labelled B5 use the Japanese JIS size of 182 × 257 mm, so measure the actual product when buying refills or covers.
B6
ISO B6 is 125 × 176 mm. It suits pocket books, compact journals and small manuals. As with B5, notebook and publishing markets may use regional or proprietary variants.
Choosing between these sizes
- Choose B3 when display impact or detailed diagrams matter.
- Choose B4 for a large publication or premium presentation format.
- Choose B5 for readable, portable books and notebooks.
- Choose B6 for genuinely compact publications with limited text and careful typography.
Printing and binding
Books and booklets need more than a trim size. Binding method, page count, paper bulk, grain direction, inner margin and printer equipment all affect the result. Ask the chosen printer for a template before final layout, particularly for perfect binding or hardback production.
Frequently asked questions
Is ISO B5 the same as JIS B5?
No. ISO B5 is 176 × 250 mm; JIS B5 is 182 × 257 mm.
Which is closest to A5?
B6 is smaller than A5 and B5 is larger than A5. B5 is often selected when A5 feels slightly cramped.
Can these sizes be folded from one another?
Each B size halves to the next B size in nominal area, but production folds require allowance for creep, trimming and grain direction.
Common mistakes to avoid
- Entering rounded inch conversions when exact millimetres are available.
- Confusing finished trim with bleed or parent-sheet dimensions.
- Allowing the printer driver to scale automatically.
- Assuming a named size is identical in every national standard.
- Ordering paper before checking the printer’s minimum, maximum and supported weight.
- Judging readability only on a zoomed computer display.
For B3, B4, B5 and B6 Paper Sizes, the most dependable approach is to retain the standard’s controlling unit, state the dimensions in the purchase order, use a supplier template and approve a full-size proof. This is especially important when the project moves between countries, software packages or production methods.
How to specify the size without ambiguity
For B3, B4, B5 and B6 Paper Sizes, a reliable print specification states more than the familiar format name. Give the finished width and height, measurement unit, orientation, number of pages or panels, paper weight, surface, colour process, bleed, finishing and quantity. This prevents regional names and printer defaults from silently changing this particular job.
- Finished size: write width × height and identify portrait or landscape.
- Artwork size: distinguish the trimmed page from any larger bleed canvas or parent sheet.
- Stock: specify grammage or basis weight, coating, colour and recycled or certified requirements.
- Finishing: state folds, scoring, binding, drilling, corner rounding, lamination or mounting.
- Tolerance: ask the supplier what cutting, folding and registration variation should be expected.
When ordering B3, B4, B5 and B6 Paper Sizes, a short name alone leaves important decisions unstated. A specification such as “finished size as stated above; portrait; 3 mm bleed; 170 gsm uncoated white stock; full colour both sides; scored where shown” is harder to misinterpret. When the format has regional variants, include the governing standard or exact dimensions every time.
Make a full-size physical proof
Screens do not communicate the physical scale of B3, B4, B5 and B6 Paper Sizes reliably. Before a large order, print a representative page at 100%, trim it to the stated size and use it as the finished item will be used. Measure one horizontal and one vertical feature with a ruler. Fold it, place it in its envelope or holder where relevant, view it from the intended distance and ask someone unfamiliar with the design to find the main information.
A proof of B3, B4, B5 and B6 Paper Sizes should check more than spelling. Look for text that is technically present but difficult to read, lines that sit too close to the trim, images whose important details enter a fold or binding area, barcodes or QR codes that do not scan, and stocks that crack or show through. For colour-critical work, a calibrated contract proof or press proof is more informative than an office print.
Sources and standards
The measurements and production guidance in this guide were checked against the following standards bodies, postal operators and print-platform specifications. Standards can be revised or withdrawn, so check the linked record when a contractual or regulated specification matters.