By Ahsan Khowaja · Updated 27 October 2026
How to use the poster size calculator
There are two modes:
- Pixels needed for a poster size. Choose a standard poster (11 × 17, 12 × 18, 18 × 24, 24 × 36, 27 × 40, 36 × 48 in, or A3 to A0), or type a custom size in inches or centimetres. Enter the print resolution in pixels per inch (PPI). You get the pixel dimensions, the megapixels, the aspect ratio and a table of every standard poster at that resolution.
- Which poster sizes my image can make. Enter your image's width and height in pixels. You get the largest listed poster it fills at 100 PPI or better, its size at 150 and 100 PPI, and a table showing the PPI it reaches on each poster.
Both modes ask for a viewing distance: how far away people will normally stand. The calculator turns it into the resolution at which a viewer with 20/20 eyesight can no longer pick out single pixels. That is the number that tells you how low you can go on a large poster.
The formula
Pixels = poster size in inches × PPI, for the width and the height separately.
A 24 × 36 in poster at 150 PPI needs 24 × 150 = 3,600 by 36 × 150 = 5,400 pixels, which is 19.44 megapixels. For centimetres, divide by 2.54 first: a 50 × 70 cm poster is 19.69 × 27.56 in, so at 150 PPI it needs 2,953 × 4,134 px.
The A sizes are defined in millimetres by ISO 216, so they come out as uneven pixel counts. A2 is 420 × 594 mm, or 16.54 × 23.39 in; at 150 PPI that is 2,480 × 3,508 px. A0 is 841 × 1189 mm, so the A0 poster size in pixels at 100 PPI is 3,311 × 4,681.
How much resolution a poster really needs
Small prints are held in the hand and looked at from about 30 cm, so 300 PPI is the usual target. Posters are looked at from further away, and the eye's ability to see detail falls with distance. A common way to put a number on that is the 1-arcminute rule: 20/20 vision separates details about 1/60 of a degree apart (Wikipedia: visual acuity). The resolution at which one pixel spans exactly that angle is:
PPI where pixels disappear = 1 ÷ (distance in inches × tan(1/60°)) ≈ 3,438 ÷ distance in inches
| Viewing distance | PPI where pixels disappear |
|---|---|
| 12 in (30 cm) | 286 PPI |
| 24 in (61 cm) | 143 PPI |
| 36 in (91 cm) | 95 PPI |
| 60 in (1.5 m) | 57 PPI |
| 120 in (3 m) | 29 PPI |
So a poster that people read from about a metre away looks fully sharp at around 100 PPI, and a banner seen from across a hall needs far less. These are estimates for average eyesight, not a printing standard. People walk up to posters they find interesting, and fine text and hard edges show low resolution sooner than photos do. If your print service publishes its own file requirements, follow those.
Poster size in pixels: chart
| Poster | Size in cm | At 100 PPI | At 150 PPI | At 300 PPI |
|---|---|---|---|---|
| 11 × 17 in (Tabloid) | 27.9 × 43.2 | 1,100 × 1,700 | 1,650 × 2,550 | 3,300 × 5,100 |
| A3 (297 × 420 mm) | 29.7 × 42 | 1,169 × 1,654 | 1,754 × 2,480 | 3,508 × 4,961 |
| 12 × 18 in | 30.5 × 45.7 | 1,200 × 1,800 | 1,800 × 2,700 | 3,600 × 5,400 |
| A2 (420 × 594 mm) | 42 × 59.4 | 1,654 × 2,339 | 2,480 × 3,508 | 4,961 × 7,016 |
| 18 × 24 in | 45.7 × 61 | 1,800 × 2,400 | 2,700 × 3,600 | 5,400 × 7,200 |
| A1 (594 × 841 mm) | 59.4 × 84.1 | 2,339 × 3,311 | 3,508 × 4,967 | 7,016 × 9,933 |
| 24 × 36 in | 61 × 91.4 | 2,400 × 3,600 | 3,600 × 5,400 | 7,200 × 10,800 |
| 27 × 40 in | 68.6 × 101.6 | 2,700 × 4,000 | 4,050 × 6,000 | 8,100 × 12,000 |
| A0 (841 × 1189 mm) | 84.1 × 118.9 | 3,311 × 4,681 | 4,967 × 7,022 | 9,933 × 14,043 |
| 36 × 48 in | 91.4 × 121.9 | 3,600 × 4,800 | 5,400 × 7,200 | 10,800 × 14,400 |
For 24x36 poster pixels, the common answer is 3,600 × 5,400 at 150 PPI; 7,200 × 10,800 at 300 PPI is a 78-megapixel file that few cameras produce. For 18x24 poster pixels, 2,700 × 3,600 at 150 PPI is the usual target, and 5,400 × 7,200 at 300 PPI (38.88 MP) if it will be seen up close.
Standard poster sizes in inches and cm
Common poster sizes fall into two families:
- US sizes in inches: 11 × 17 (Tabloid, also used for flyers), 12 × 18, 18 × 24, 24 × 36, and 27 × 40, which is the usual size of a US movie poster ("one-sheet"). 36 × 48 is used for large display boards.
- ISO A sizes: each A size is half the one above it, and all share the same shape (1:1.414). A0 has an area of one square metre. The standard poster size in cm for each is A3 29.7 × 42, A2 42 × 59.4, A1 59.4 × 84.1 and A0 84.1 × 118.9.
The two families have different shapes. 24 × 36 is 2:3, the same as a camera photo, while 18 × 24 is 3:4, the same as most phone photos. An A-size poster is in between, so both kinds of photo lose a little to cropping. The aspect ratio calculator shows exactly how much.
Checking your image: which posters it can make
In the second mode the calculator fits your image to each poster, long side to long side, and reports the lower of the two resolutions, because that is the side that limits the print:
- A 6000 × 4000 px camera photo (24 MP) reaches 111 PPI on a 36 × 48 in poster, and 167 PPI on 24 × 36.
- A 4032 × 3024 px phone photo (12 MP) reaches 101 PPI on a 27 × 40 in poster but only 86 PPI on A0.
- A 1920 × 1080 px image, such as a video frame or a screenshot, can't reach 100 PPI even on an 11 × 17 in poster, because 1,080 ÷ 11 = 98. At 100 PPI it covers only 19.2 × 10.8 in.
Upscaling software can increase the pixel count, but it can't recover detail the camera didn't capture. For photo prints of 4 × 6 to 20 × 30 in at 300 PPI, use the print size calculator. For a print stretched over a frame, with extra image around the edges, use the canvas size calculator.
Posters for screens and social media
A poster that will only be shown on screens doesn't need a PPI at all, only a pixel size. Poster size in pixels for Instagram is set by the platform's post shapes, such as 1080 × 1350 for a 4:5 portrait post; see our guide to Instagram image sizes for the current list. If the same design will also be printed, design it at the print size first and make the social version with the image resizer, since scaling down loses nothing and scaling up can't add detail.
