The Pixel Calculator – the precise tool for image editing, photography, and printing. Quickly and accurately calculate the relationship between image resolution (pixels, Mpx), print size (mm, cm, inches) and pixel density (dpi, ppi). Perfect for photographers, designers, and anyone working with digital images.
Formulas Examples Units Printing Standards
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Ratio
Given ratio:
Infoi
| Total Pixels | × = Mpx |
|---|---|
| Image Size | × mm |
| DPI / PPI | |
| Aspect Ratio | x:y |
| Color Depth | |
| File Size (TIF) | |
| File Size JPG (80%) | |
| Pitch | μm |
| Pixel Size | μm² |
sponsored by: Dia Foto Film Scannen www.archivscan.ch
Formulas
Key terms explained briefly:
DPI refers to print dot density (Dots per Inch)
PPI refers to digital resolution in pixels per inch
Understanding the difference is essential for proper image preparation.
Calculation of length or width, pixels and DPI with the following parameters:
Image
3273×2445 Pixel (8Mpx, 4:3)
Print Size
10.91 × 8.15 in
Pixel Density
300dpi
File Size
TIF Color RGB in MB
Basic formula: How do I calculate the print size in inches
Length[in] = pxdpi
Example: Image width 3273 px at 300 dpi
Length[in] = 3273300 = 10.91 in
Basic formula: How do I calculate the pixels
Pixel = dpi × Length[in]
Example (approximation)
Pixel = 300 × 10.91 = 3273 px
Basic formula: How do I calculate the dpi
dpi = PixelLength[in]
Example
dpi = 327310.91 = 300 dpi
Basic formula: How do I calculate the file size
Size[MB] = Width × Height × 248 × 1M
Example
Size[MB] = 3273 × 2445 × 248 × 1M = 24MB
Examples
I want to print a photo in 5 × 7 inch format at high quality. What resolution in pixels is required?
A high-quality photo is printed at 300 dpi. To calculate the resolution in megapixels, multiply the number of pixels in width and height and then divide by one million.
Pixel X = 300 × 5 = 1500 px
Pixel Y = 300 × 7 = 2100 px
Resolution = 1500 × 21001000000 = 3.15 Mpx
I have an image with 3264 × 2448 pixels and want to print it as a poster. How large can the poster be printed?
Unlike a small photo album image, a poster does not require high pixel density since it is viewed from a distance. Approximately 100 dpi is recommended for posters.
Length[in] = 3264100 = 32.64 in
Width[in] = 2448100 = 24.48 in
I want to scan slides and present them in a slideshow on a TV. TV screen 40 inches; Resolution: 1920 × 1080 pixels. What should be the scan resolution?
A slide measures 1.417 × 0.945 inches. The aspect ratio does not match that of the TV (16:9 vs. 3:2), so we only calculate the pixel density for the height.
dpi = 1080 × 10.945 = 1143 dpi
Resulting image width in the correct aspect ratio:
px = 1143 × 1.417 = 1620 px
I want to print a slide as a poster with maximum resolution at a size of 35.43 × 23.62 inches. What will be the quality in dpi?
The scanner's maximum resolution is 4000 dpi. A slide measures 1.417 × 0.945 inches. After calculating the number of pixels, the pixel density for the poster can be determined.
Pixel = 4000 × 1.417 = 5668 px
dpi = 566835.43 = 160 dpi
Units of Measurement
| English Unit | 1 inch = 25.4 mm |
| Dots per Inch (dpi) | 1 dpi = 1 dot per inch = 1 dot per 25.4 mm |
| Pixels per Inch (ppi) | 1 ppi = 1 pixel per inch = 1 pixel per 25.4 mm |
| Digital Units | 1 bit = 0 or 1 1 Byte (B) = 8 bit 1 kB = 1024 B 1 MB = 1024 kB |
Standard Print Resolutions for Consumer Photo Services
Many international photo services and labs use professional digital printing systems such as the Fujifilm Frontier series, Noritsu Drylabs or Canon PRO/Maxify systems. These are used worldwide in photo printing – both in the consumer sector and in professional segments. They are usually printed on high-quality photo paper such as Fujicolor Crystal Archive or similar materials.
Print resolution – measured in DPI (dots per inch) – is crucial for image quality. The smaller the format or the shorter the viewing distance, the higher the DPI value should be. For large-format prints, a lower DPI value is acceptable since they are viewed from a greater distance.
Well-known International Photo Services
The following providers are leading worldwide or in Europe in the field of online photo printing and adhere to the standards mentioned above:
- CEWE – One of the world's largest photo services, active in over 20 countries (often under local brands such as dm-Fotoparadies, Müller, Saturn, etc.)
- Shutterfly – Market leader in the USA, offering a comprehensive range of photo and gift products
- Snapfish – Internationally active (USA, UK, Australia), known for fast consumer printing
- Photobox – A large platform focused on the UK, France, and Europe
- Pixum – Leading online photo service in the German-speaking region (Germany / Europe)
- ifolor – A Swiss quality provider with market presence throughout the EU
- WhiteWall – Specialist in gallery and fine art prints, with international shipping
- Mpix – A high-quality provider in the USA, popular among professional and portrait photographers
Many of these providers automatically check the resolution of your image file during upload and provide guidance on whether the chosen print format is suitable. The values in the table below correspond to the requirements of these platforms.
Common Resolutions by Format Size
- 300 DPI for photo prints, postcards, and small posters
- 200–250 DPI for medium poster formats up to approximately 20×30 inches
- 150 DPI for large posters and wall art (e.g., 32×47 inches)
- 72–100 DPI for XXL formats such as advertising banners or posters
Print Formats with Recommended Resolution
| Format (W × H in, exact) | Common Name | Recommended DPI | Typical Use | Pixels (W × H) |
|---|---|---|---|---|
| 2 × 3 in | Wallet Size | 300 | Passport, Wallet photos | 600 × 900 |
| 4 × 6 in | Standard Print (4R) | 300 | Photo prints | 1200 × 1800 |
| 5 × 7 in | 5R | 300 | Photo prints, Framed photos | 1500 × 2100 |
| 8 × 10 in | Classic Enlargement | 300 | Framed portraits | 2400 × 3000 |
| 8.5 × 11 in | US Letter | 300 | Photo documents, portfolios | 2550 × 3300 |
| 11 × 14 in | Large Print | 250 | Wall display | 2750 × 3500 |
| 16 × 20 in | Poster | 200 | Posters, wall art | 3200 × 4000 |
| 18 × 24 in | Medium Poster | 200 | Displays, graphics | 3600 × 4800 |
| 20 × 30 in | Large Poster | 150 | Event posters | 3000 × 4500 |
| 24 × 36 in | Movie Poster | 150 | Promotional display | 3600 × 5400 |
| 36 × 48 in | Exhibition Print | 100 | Posters, Banners | 3600 × 4800 |
| > 36 × 48 in | Billboard / Large Format | 72–100 | Billboards, large displays | varies |
