Convert between pixels, inches, millimetres, and centimetres for any resolution. Perfect for print preparation and screen design.
DPI (dots per inch) and PPI (pixels per inch) both measure resolution - How many dots or pixels fit into one inch. Higher values mean more detail per inch. For web and screen use, the DPI value is largely irrelevant because browsers display images at 1:1 pixels regardless. For print, 300 DPI is the standard for sharp, photo-quality output. The key formula is simple: Pixels = Inches × DPI.
Pixels ↔ Inches ↔ DPI
Presets:
Formula: Inches = Pixels ÷ DPI · mm = Inches × 25.4 · cm = mm ÷ 10
Presets:
Formula: Pixels = Inches × DPI
Quick Pixels ↔ mm & cm
Millimetres (mm)
— mm
Centimetres (cm)
— cm
Formula: mm = (Pixels ÷ DPI) × 25.4
DPI Reference Guide
use case & quality
Use Case
DPI
Quality
Notes
Web / Screen (standard)
72
Historical default for Mac displays. The DPI tag in image files has no effect on on-screen pixel size - Only pixel dimensions matter.
Screen (Windows default)
96
Windows default screen resolution. Commonly used as the base for web images. DPI metadata is still ignored by browsers.
Retina / HiDPI
144+
Retina displays pack 2× more physical pixels per CSS pixel. Provide @2x images (double the pixel dimensions) for crisp display.
Draft Print
150
Acceptable for internal documents, proofs, and low-cost inkjet prints. Visible softness at close range.
Standard Print
300
Industry standard for photos, brochures, flyers, and marketing materials. Sharp detail at normal viewing distance.
High-Quality Print
600
Fine art reproduction, archival prints, and laser printing. Requires very large pixel dimensions - Significant file sizes.
Common Print Sizes
pixels at 300 & 150 dpi
A4
210 × 297 mm (8.27 × 11.69 in)
300 DPI2480 × 3508 px
150 DPI1240 × 1754 px
US Letter
8.5 × 11 in (216 × 279 mm)
300 DPI2550 × 3300 px
150 DPI1275 × 1650 px
A3
297 × 420 mm (11.69 × 16.54 in)
300 DPI3508 × 4961 px
150 DPI1754 × 2480 px
4 × 6 in
102 × 152 mm (standard photo)
300 DPI1200 × 1800 px
150 DPI600 × 900 px
5 × 7 in
127 × 178 mm (portrait print)
300 DPI1500 × 2100 px
150 DPI750 × 1050 px
8 × 10 in
203 × 254 mm (large photo)
300 DPI2400 × 3000 px
150 DPI1200 × 1500 px
DPI vs PPI Explained
PPI (pixels per inch) refers to the density of pixels in a digital image or display. It describes how many pixels exist per linear inch. A 300 PPI image has 300 pixels packed into every inch of its width and height. PPI is a property of the digital file or screen - It's relevant when preparing images for print because it determines the physical size the image will reproduce at.
DPI (dots per inch) technically refers to the output resolution of a printer - How many physical ink dots the printer lays down per inch. A modern inkjet printer may use 1440 or 2880 physical dots per inch to render an image that's only 300 PPI. The extra dots create smooth colour gradients through dithering patterns. In practice, DPI and PPI are used interchangeably in everyday conversation, and most software (Photoshop, Lightroom, etc.) uses the terms synonymously when talking about image resolution.
The practical takeaway: set your image to 300 PPI before sending to a print lab, and make sure the pixel dimensions are large enough at that resolution (e.g. an A4 print at 300 DPI needs 2480 × 3508 pixels minimum). If your image is too small, either print at a smaller physical size or accept softer output. Upscaling a low-resolution file does not add real detail - It only inflates the file size. Use the Image File Size Calculator to estimate how large the file will be at your chosen dimensions and format before exporting.
Frequently Asked Questions
300 DPI is the standard for photo-quality printing. At this resolution, the human eye cannot distinguish individual dots at a normal viewing distance of about 30 cm. For large-format prints viewed from further away (posters, banners), 150 DPI is often sufficient. For archival or fine-art printing, 600 DPI may be requested.
No - For web display, DPI (the metadata tag embedded in the file) is completely ignored by web browsers. Browsers render images based on pixel dimensions only, not the embedded DPI value. Whether your image says 72 DPI or 300 DPI, it will display at the same pixel size on screen. DPI only becomes relevant when the file is sent to a printer or opened in print-layout software like InDesign. For web use, focus on pixel dimensions and file size - Use our JPG compressor to reduce file size without changing pixel dimensions, and use the Format Comparison tool to see how JPG, PNG, and WebP trade off size and quality for your specific image.
Multiply the physical size in inches by the DPI. For example, an 8×10 inch print at 300 DPI needs 8×300 = 2400 pixels wide and 10×300 = 3000 pixels tall. Use the "Size + DPI → Pixels" mode in the calculator above to do this automatically for any combination of dimensions and resolution.
You can change the DPI metadata tag without altering pixels (this changes physical print size only, not the actual image data). However, to genuinely increase resolution - Adding real pixel detail - You would need to resample the image, which involves interpolation (upscaling) and does not recover lost information. AI-based upscaling tools can produce better results than traditional bicubic interpolation, but the detail is synthesized, not recovered.
At 72 DPI, an image prints much larger than at 300 DPI. For example, a 1440×900 pixel image printed at 72 DPI would be 20×12.5 inches. The same image at 300 DPI would print at only 4.8×3 inches - But it would be sharp. If you enlarge the 72 DPI version to the same physical size as a 300 DPI print, the quality drops significantly because there aren't enough pixels to fill the space without visible softening or pixelation.
Modern smartphones embed a DPI tag of 72 or 96 in JPEG files by default, but the actual pixel count is much higher. An iPhone 15 shoots at 12 MP (4032×3024 pixels). Despite the 72 DPI tag, those dimensions are sufficient for a 13.4×10.1 inch print at 300 DPI. The tag is just metadata - Check the actual pixel count, not the embedded DPI, to judge print suitability. You can verify your image's pixel dimensions and metadata with our Image Metadata Viewer. Once you have a print-ready file, use the Photo Editor to crop and resize it to exact print dimensions.
