FREE POSTER PRINT TOOL
Poster Size & Aspect Ratio Calculator
Upload an image to check its aspect ratio, maximum print size at 300 DPI and compatibility with A4, A3, A2, A1, 30 × 40 cm, 40 × 50 cm, 50 × 70 cm, 60 × 90 cm, 18 × 24 in and 24 × 36 in poster sizes.
Poster size compatibility
Compare your image with common poster and print formats.
POSTER CALCULATOR
How to use the poster size calculator
Choose an image from your device. The poster size calculator reads the image dimensions directly in your browser and calculates the image aspect ratio, maximum print size at 300 DPI and compatibility with common poster formats.
Upload an image
Choose a JPG, PNG, WEBP or GIF image from your device.
Check image details
See the pixel dimensions, simplified aspect ratio and estimated 300 DPI print size.
Compare poster sizes
Check whether each supported poster format is an exact fit, good fit or requires cropping.
IMAGE PROPORTIONS
Check image aspect ratio for poster printing
Image aspect ratio describes the relationship between image width and height. Common poster aspect ratios include 2:3, 3:4 and the ISO A-series ratio used by A4, A3, A2 and A1 paper sizes.
When the aspect ratio of an image closely matches a poster format, less cropping is required. The calculator labels each poster size as an exact fit, good fit or crop needed so you can compare formats before preparing an image for print.
IMAGE RESOLUTION
Maximum print size at 300 DPI
The 300 DPI print size calculation uses the pixel dimensions of your image to estimate its maximum physical dimensions at 300 dots per inch.
Divide the pixel width and height by 300 to calculate the size in inches, then convert inches to centimetres. Aspect ratio compatibility and image resolution are separate checks: an image can match a poster shape but still have limited pixel dimensions for a large print.
SIZE COMPATIBILITY
Poster sizes checked by the calculator
Compare your image with ISO A-series formats, popular metric poster dimensions and common inch-based poster sizes.
QUICK ANSWERS
Poster size calculator FAQ
What poster size fits my image?
Upload your image to compare its aspect ratio with A4, A3, A2, A1, 30 × 40 cm, 40 × 50 cm, 50 × 70 cm, 60 × 90 cm, 18 × 24 in and 24 × 36 in poster sizes.
How do I calculate print size at 300 DPI?
Divide the image width and height in pixels by 300. The result gives the maximum dimensions in inches at 300 DPI. This calculator also converts the result to centimetres.
What does crop needed mean?
Crop needed means the image aspect ratio differs from the selected poster format. Part of the image may need to be removed to fill the complete poster dimensions without empty space.
What is an exact poster size fit?
An exact fit means the image and poster format use the same or an effectively identical aspect ratio according to the calculator comparison.
Does the calculator upload my image?
No. Image dimensions are read locally in your browser. The calculator does not upload the selected image to a server.
Can I check A4, A3, A2 and A1 poster sizes?
Yes. The calculator checks A4, A3, A2 and A1 aspect ratio compatibility alongside popular metric and inch-based poster sizes.