Poster Print Size Calculator
Scaling a Photo Up Without Distorting It
Enlarging an image for a poster means picking one dimension — width or height — and letting the other follow automatically to preserve the original aspect ratio, otherwise the image stretches or squashes. This calculator locks the aspect ratio from the source pixel dimensions and solves for the matching print size and the resulting DPI, so you know both the final poster size and how sharp it will actually look before sending it to print.
The Formula
Solving from width: Height = Width / Aspect Ratio, DPI = Pixel Width / Print Width
Solving from height: Width = Height × Aspect Ratio, DPI = Pixel Height / Print Height
Where This Calculation Matters
- Large-format printing — determining the biggest poster size a photo supports before quality visibly drops.
- Gallery and exhibition prints — balancing desired print size against the DPI needed for close-up viewing.
- Marketing and event signage — scaling a logo or photo asset to a required poster width while keeping proportions correct.
- Photo enlargement services — setting customer expectations about output quality at a requested print size.
Worked Example
A 24-megapixel image (6000 × 4000 px) scaled to a 24 in wide poster:
| Quantity | Value |
|---|---|
| Resulting height | 16.0 in |
| Resulting DPI | 250 DPI |
250 DPI at typical poster viewing distance (several feet away) reads as sharp; the same file pushed to 300 DPI for close viewing would need a smaller print size.
How to Use This Calculator
- Choose a mode: solve from a target width or a target height.
- Enter the image width and height in pixels.
- Enter your desired print width (or height) in inches.
- Select Calculate to get the matching dimension and the resulting DPI.
Related Calculations
To check whether a given print size meets a specific minimum DPI requirement, use the Print Resolution Calculator. For the paper stock that poster will be printed on, see the Paper Weight Calculator.