An A3 poster has approximately twice the area of A4, and A2 has approximately twice the area of A3. Each step is a clear increase on the wall, even though neither edge doubles in length.
| Poster size | Portrait dimensions | Landscape dimensions |
|---|---|---|
| A4 | 21 × 29.7 cm | 29.7 × 21 cm |
| A3 | 29.7 × 42 cm | 42 × 29.7 cm |
| A2 | 42 × 59.4 cm | 59.4 × 42 cm |
The dimensions describe the paper. A frame or mount will make the finished display larger, so measure the complete arrangement if you are filling a particular space.
Start with where the print will go
A4 is worth trying for a smaller wall area or a print viewed at close range. A3 gives the photograph more presence without taking the same space as A2. A2 makes a larger feature, but its suitability depends on both the wall and the image.
Those are starting points rather than room-size rules. Use sheets of paper to mock up the dimensions and view them from where you normally stand or sit. If a frame is already waiting, its required print size should lead the decision.
Check whether your photo fits an A size
A-series paper has a consistent shape, but phone and camera photographs use several different proportions. A 4:3 photo will not fill an A-size sheet exactly without cropping or a border treatment. The preview should make the chosen result clear.
Switching between portrait and landscape reverses the dimensions; it does not make a wide photograph naturally fit a tall sheet. Keep the subject inside the crop and avoid choosing a size solely by its name.
Choose the file before the largest size
Use the best available original. Enlarging makes blur and compression easier to notice, especially when the poster will be examined close up.
Compare current poster sizes and prices. Choose the size that fits your photograph and display, rather than assuming the largest option is always the best one.