Resolution (DPI/PPI)

Image resolution and its relationship to print quality.

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Core Concepts

DPI (Dots Per Inch)

The number of dots per inch in print. Determines the quality of physical output.

PPI (Pixels Per Inch)

The number of pixels per inch in a digital image. Determines on-screen display quality.

Note: In practice, DPI and PPI are used interchangeably. The term "DPI" is standard for print.

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Resolution Guide

Usage	Minimum DPI	Recommended DPI
Web/Screen	72	72–96
Office print	150	200
Professional print	300	300–350
Large format (billboard)	72–150	100–150

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Why 300 DPI?

            72 DPI              150 DPI             300 DPI
         ┌─────────┐         ┌─────────┐         ┌─────────┐
         │ █ █ █ █ │         │█ █ █ █ █│         │█████████│
         │ █ █ █ █ │         │█ █ █ █ █│         │█████████│
         │ █ █ █ █ │         │█ █ █ █ █│         │█████████│
         │ █ █ █ █ │         │█ █ █ █ █│         │█████████│
         └─────────┘         └─────────┘         └─────────┘
           Pixelated           Medium quality       Sharp

The human eye cannot distinguish detail above 300 DPI from a distance of approximately 30 cm. As a result:

• 300 DPI is the standard for hand-held materials (business cards, brochures)
• 150 DPI is sufficient for posters and banners
• 72 DPI is for screens only

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Resolution Calculation

Formula

Pixels = Inches × DPI
or
Pixels = (mm ÷ 25.4) × DPI

Example: A4 Print

A4 size: 210 mm × 297 mm

Required pixels at 300 DPI:

Width:  (210 ÷ 25.4) × 300 = 2,480 pixels
Height: (297 ÷ 25.4) × 300 = 3,508 pixels

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Common Sizes

Minimum Pixel Values (at 300 DPI)

Product	Size (mm)	Minimum Pixels
Business Card	85×55	1,004×650
A5 Flyer	148×210	1,748×2,480
A4	210×297	2,480×3,508
A3	297×420	3,508×4,961
A2 Poster	420×594	4,961×7,016

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Checking Resolution

How to Check

Photoshop:

Image → Image Size → Resolution

Illustrator:

File → Document Setup → Raster Effects → Resolution

NowToPrint: Automatic check is performed during upload:

• 300+ DPI: Sufficient
• 150–299 DPI: Warning
• Below 150 DPI: Error

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Can Resolution Be Increased?

Upscaling Limitations

Enlarging a low-resolution image with software does not add real detail:

Original 72 DPI → Software upscaled to 300 DPI = Blurry 300 DPI

AI Upscaling

AI-based tools produce better results, however:

• Output is not as sharp as the original
• Detail loss is possible
• Still risky for professional print

Recommended: Use the original high-resolution source file.

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Large Format Print

Why Is Lower DPI Sufficient?

Large formats such as posters and billboards are viewed from a distance:

Distance	Required DPI
30 cm (business card)	300 DPI
1 metre	150 DPI
3 metres	72 DPI
5+ metres	50 DPI sufficient

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Summary

┌─────────────────────────────────────────┐
│  FOR PRINT-READY FILES:                 │
│   Minimum 300 DPI                     │
│   CMYK colour mode                    │
│   3 mm bleed                          │
│   At original size                    │
└─────────────────────────────────────────┘

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