How do I check image dimensions and resolution?

Drag and drop any image file (JPEG, PNG, WebP, GIF, SVG, AVIF) into the inspector. The tool reads header metadata and raster dimensions instantly, showing pixel width, height, total megapixels (Width × Height / 1,000,000), aspect ratio, and diagonal pixels.

What is the difference between DPI and PPI?

PPI (Pixels Per Inch) measures digital image pixel density on screen displays. DPI (Dots Per Inch) refers to physical ink droplet density in commercial printing. While used interchangeably, an image requires 300 DPI for tack-sharp photographic print reproduction.

How does the Image Alpha Channel Checker detect transparency?

The inspector loads the image onto an off-screen HTML5 canvas and analyzes the 8-bit alpha byte (values 0 to 255) of each pixel. If any pixel contains an alpha value below 255, the tool reports transparency presence, calculates the exact percentage of transparent pixels, and renders an isolated alpha matte.

How is JPEG compression quality estimated?

The tool parses the JPEG binary stream to locate the DQT (Define Quantization Table) markers. By averaging the luminance quantization matrix coefficients and comparing them to standard Independent JPEG Group (IJG) tables, it accurately estimates the save quality factor (1% to 100%).

Image Size, Dimension, Resolution & DPI Inspector

Image Source & Ingest

JPEG • 24.0 MP

Drop your image here or click to browse

Supports JPEG, PNG, WebP, GIF, BMP, TIFF, SVG, AVIF

Instant Preset Samples Test without uploading

Manual Dimension Solver Simulate hypothetical resolutions

Width (Pixels)

Height (Pixels)

Target Print DPI

Color Space

DIMENSIONS

Dimensions

6,000 × 4,000

Aspect Ratio: 3:2 (1.50) • Landscape

FILE SIZE

File Size

7.42 MB

7,781,248 bytes • 0.31 bytes/pixel

Resolution

24.0 MP

24,000,000 pixels • 6K UHD Category

Format & Depth

JPEG • 24-bit

8 bits/channel (RGB) • 16.7M Colors

Print Size @ 300 DPI

20.0 × 13.3 in

50.8 × 33.9 cm • 300 DPI metadata

Alpha & Quality

Q92 • Opaque

0% Transparent pixels • DQT Q-Factor ~92%

Image Viewport & Transparency Inspector

6000 × 4000 px • Alpha: None (Opaque)

Cursor: X: 0, Y: 0

Color: RGBA(0, 0, 0, 1.0)

Aspect Ratio: 3:2 (1.50)

Physical Print Dimension Benchmarks

Max Sharp Print: 20" × 13.3" @ 300 DPI

300 DPI (Gallery Print)

20.0" × 13.3"

50.8 × 33.9 cm

240 DPI (Fine Photo)

25.0" × 16.7"

63.5 × 42.3 cm

150 DPI (Magazine / Poster)

40.0" × 26.7"

101.6 × 67.7 cm

72 DPI (Web Screen)

83.3" × 55.6"

211.7 × 141.1 cm

Complete Technical Inspection Matrix

17 Properties Verified

Property	Inspected Value	Category	Standard & Technical Detail

Complete Image Inspection & Technical Metadata Guide

Digital image files carry critical spatial, tonal, and colorimetric data. Understanding pixel dimensions, color depth, alpha channels, and print resolution ensures your visual assets reproduce flawlessly across print media, mobile displays, and web platforms.

1. Calculating Image Megapixels & Aspect Ratios

Image resolution is defined by the total count of discrete color sensors or raster pixels across width and height:

Total Pixels = Pixel Width × Pixel Height
Megapixels (MP) = Total Pixels / 1,000,000
Aspect Ratio = Width / Height (Simplified using Greatest Common Divisor GCD)
Diagonal Pixels = √(Width² + Height²)

For example, a standard 24MP full-frame image measuring 6,000 × 4,000 pixels has an aspect ratio of 3:2 (1.50), exactly matching classic 35mm film.

2. Color Depth vs. Bit Depth

Bit depth specifies the number of binary bits utilized to represent the color of a single pixel or channel:

24-bit TrueColor (8 bits per channel): 256 red × 256 green × 256 blue = 16,777,216 distinct colors. Standard for Web, JPEG, and sRGB.

32-bit RGBA: 24-bit RGB TrueColor plus an 8-bit Alpha transparency mask channel (256 levels of opacity).

30-bit Deep Color (10 bits per channel): 1,024 levels per channel = 1.07 billion colors. Standard for HDR10 and modern HEIF.

48-bit (16 bits per channel): 65,536 levels per channel. Essential in RAW processing, TIFF, and PSD to avoid gradient posterization during color grading.

3. DPI vs. PPI: Print Sizing Equations

A digital image does not possess physical inches or centimeters until assigned a print resolution (DPI/PPI):

Physical Width (inches) = Pixel Width / Print DPI
Physical Height (inches) = Pixel Height / Print DPI
Standard Photo Print Quality: 300 DPI (6000 × 4000 px → 20" × 13.3" / 50.8 × 33.9 cm)

4. JPEG Quantization & Quality Analysis

JPEG is a lossy transform codec utilizing the Discrete Cosine Transform (DCT). During compression, high-frequency spatial detail is divided by a Quantization Table (DQT). By analyzing the scaling factor applied to these quantization matrices, the original save quality (1% to 100%) can be reconstructed with high accuracy.

Frequently Asked Questions

No. If "Resample" is unchecked, changing the DPI tag simply recalculates the physical print size on paper without touching a single pixel. A 6000x4000 image has the exact same visual quality whether tagged as 72 DPI or 300 DPI on a computer screen. Only the physical print output scale changes.

An alpha channel stores transparency information. Standard RGB has 3 channels (Red, Green, Blue). An RGBA format adds an 8-bit Alpha channel where 0 is 100% transparent and 255 is 100% opaque. PNG, WebP, TIFF, and GIF support alpha transparency. JPEG files NEVER support alpha channels.

An ICC profile is a color management file that describes the color gamut and tone response of an image. Without an embedded profile, web browsers default to sRGB, which can cause images saved in wide-gamut Adobe RGB or Display P3 to appear dull, washed out, and desaturated.

Bits Per Pixel (BPP) in compression analysis represents the ratio of total file bits divided by the number of pixels (BPP = File Size in Bytes × 8 / Total Pixels). A value between 1.5 and 3.0 BPP represents high-fidelity JPEG compression, while values below 0.5 BPP signal aggressive compression with visible blocky artifacts.