Image Size Checker: How to Check Dimensions and File Size

Every image carries three measurements that matter: pixel dimensions (width × height), file size (bytes on disk), and resolution (DPI/PPI for print). Mixing them up causes rejected uploads, blurry prints, and slow web pages. Here is every reliable way to check all three — from right-clicking on your desktop to scripting batch checks across thousands of files.

What Each Measurement Actually Means

Before checking anything, know what you are looking at.

Pixel dimensions and file size are independent. A 4000×3000 PNG can be 15 MB. Compress it to WebP and it drops to 800 KB — same pixel dimensions, fraction of the file size. DPI is metadata that tells printers how large to render the image physically. On screens, it has no effect. For a deeper explanation, see our guide on what image resolution really means.

Check Image Size on Windows

Right-click the image file in File Explorer and select Properties. Under the Details tab, scroll to the Image section. You will see:

• Dimensions — pixel width × height
• Width and Height — pixel values listed separately
• Horizontal resolution and Vertical resolution — DPI

File size is on the General tab at the top. Two values appear: "Size" (actual bytes) and "Size on disk" (allocated space). Use "Size" for upload limits.

This works for JPEG, PNG, BMP, GIF, and TIFF. For WebP or AVIF, Windows 11 shows dimensions natively; Windows 10 requires a codec extension from the Microsoft Store.

Check Image Size on Mac

Select the image in Finder, then press ⌘ + I (or right-click → Get Info). The More Info section shows:

• Dimensions — pixel width × height
• Color space and Color profile
• DPI (if set in metadata)

File size appears at the top of the info panel. For a quick glance without opening Get Info, enable the Finder status bar (View → Show Status Bar) — it displays the selected file's size at the bottom of the window.

Preview.app shows dimensions in the title bar when you open the image, and Tools → Show Inspector (⌘ + I) gives the full breakdown including DPI.

Check Image Dimensions in Browser DevTools

When you need to check the dimensions of an image on a live web page — not a file on disk — browser DevTools is the fastest path.

1. Right-click the image on the page and select Inspect (or press F12).
2. The Elements panel highlights the <img> tag. Hover over it to see a tooltip showing rendered size and intrinsic size.
3. The rendered size is what the browser displays (CSS-controlled). The intrinsic size is the actual pixel dimensions of the source file.

If the rendered size is larger than the intrinsic size, the browser is upscaling the image and it will look blurry. If the intrinsic size is much larger than the rendered size, you are serving an oversized file — compress it or resize it to save bandwidth. For more on setting image dimensions in HTML, see our HTML image dimensions guide.

Check Image Size with CLI Tools

Command-line tools are the fastest option for checking one image or scripting checks across entire directories.

file (Pre-installed on macOS/Linux)

file photo.png
# Output: photo.png: PNG image data, 1920 x 1080, 8-bit/color RGBA, non-interlaced

Shows pixel dimensions and color depth. Does not show file size — pair it with ls -lh or stat for that.

ImageMagick identify (v7.1)

# Install: brew install imagemagick (macOS) or apt install imagemagick (Debian/Ubuntu)
identify photo.png
# Output: photo.png PNG 1920x1080 1920x1080+0+0 8-bit sRGB 2.45MB 0.010u 0:00.010

identify -verbose photo.png | grep -E "Geometry|Filesize|Resolution|Units"
# Geometry: 1920x1080+0+0
# Resolution: 72x72
# Units: PixelsPerInch
# Filesize: 2.45MB

ImageMagick identify (v7.1) gives dimensions, file size, resolution, color space, and compression in one command. The -verbose flag dumps every metadata field the file contains.

exiftool (v12.87)

# Install: brew install exiftool (macOS) or apt install libimage-exiftool-perl (Debian/Ubuntu)
exiftool -ImageSize -FileSize -XResolution -YResolution photo.jpg
# Image Size: 1920x1080
# File Size: 342 kB
# X Resolution: 72
# Y Resolution: 72

ExifTool (v12.87) excels at reading embedded metadata — EXIF, IPTC, XMP — across nearly every image format. Use it when you need DPI, camera model, GPS coordinates, or color profile data alongside dimensions.

ffprobe (FFmpeg v7.0)

ffprobe -v error -select_streams v:0 -show_entries stream=width,height -of csv=p=0 photo.png
# 1920,1080

Already installed if you have FFmpeg. Clean machine-readable output, ideal for piping into scripts.

Check Image Size with Python

For programmatic checks — validating uploads, processing batches, or integrating into a build pipeline — Python's Pillow library is the standard tool.

# pip install Pillow==10.4.0
from PIL import Image
import os

img = Image.open("photo.png")
width, height = img.size
file_size = os.path.getsize("photo.png")
dpi = img.info.get("dpi", (72, 72))

print(f"Dimensions: {width}x{height}")
print(f"File size: {file_size / 1024:.1f} KB")
print(f"DPI: {dpi[0]}x{dpi[1]}")

Image.open() reads only the header — it does not load the full image into memory. This means checking dimensions on a 200 MB TIFF is near-instant.

Batch Image Size Checking

When you need to check hundreds or thousands of images at once, scripting beats clicking.

Bash one-liner (ImageMagick v7.1)

identify -format "%f %wx%h %b\n" /path/to/images/*.{jpg,png,webp}

This outputs filename, dimensions, and file size for every matching image in the directory.

Python batch script (Pillow 10.4.0)

from PIL import Image
from pathlib import Path

for path in Path("images").glob("**/*"):
    if path.suffix.lower() in {".jpg", ".jpeg", ".png", ".webp", ".avif"}:
        img = Image.open(path)
        w, h = img.size
        size_kb = path.stat().st_size / 1024
        print(f"{path.name:40s} {w:5d}x{h:<5d} {size_kb:8.1f} KB")

Add filtering logic to flag images that exceed upload limits or fall below minimum dimension requirements. This is how build pipelines enforce image size standards for websites.

When Image Dimensions Matter

Different platforms enforce different size requirements. Upload an image that is too small and it gets stretched. Too large and the platform re-compresses it — destroying quality you could have controlled yourself.

Common Platform Dimension Requirements

For a complete breakdown with aspect ratios, see our social media image sizes guide. If your images do not match the target dimensions, resize them before uploading — you will get better quality than letting the platform do it for you. Need to understand aspect ratios before resizing? Use our image aspect ratio calculator.

Web Performance

For websites, file size matters more than pixel dimensions. A 5 MB hero image on a landing page adds seconds to load time. Aim for images under 200 KB on web pages. Use modern formats like WebP or AVIF — they deliver the same visual quality at 30-50% smaller file sizes than JPEG. Pixotter can convert your images to these formats entirely in the browser.

FAQ

What is an image size checker?

An image size checker is any tool that reads an image file and reports its pixel dimensions (width × height), file size (KB or MB), and optionally its resolution (DPI/PPI). Built-in OS tools, CLI utilities, and online services all serve this purpose.

How do I check the pixel dimensions of an image online?

Upload the image to Pixotter's resize tool — it displays the current dimensions immediately before you make any changes. No account required, and the image never leaves your browser.

What is the difference between image dimensions and file size?

Dimensions are the pixel count (e.g., 1920×1080). File size is the bytes stored on disk (e.g., 450 KB). A large-dimension image can have a small file size if compressed efficiently, and a small-dimension image can have a large file size if saved in an uncompressed format like BMP or TIFF.

How do I check image size on iPhone?

Open the Photos app, select the image, tap the (i) info button (or swipe up on the photo). iOS 16+ shows pixel dimensions and file size directly. For older versions, open the image in the Files app and use Get Info.

How do I check image size on Android?

Open the image in Google Photos, tap the three-dot menu, then Details. You will see pixel dimensions, file size, camera metadata, and location data. The default Files or Gallery app also shows size in file properties.

What image dimensions do I need for printing?

Multiply the desired print size in inches by 300 (the standard print DPI). A 4×6 inch print needs 1200×1800 pixels. An 8×10 inch print needs 2400×3000 pixels. Below 300 DPI, print output looks soft. Below 150 DPI, it looks pixelated. Check our DPI guide for details.

Can I check image dimensions without downloading the image?

Yes. Right-click the image in your browser, select Inspect, and hover over the <img> tag in DevTools. The tooltip shows both the rendered size and the intrinsic (original) pixel dimensions. No download needed.

Why is my image file size so large?

Common causes: uncompressed format (BMP, TIFF), excessive pixel dimensions for the intended use, embedded metadata (EXIF, ICC profiles), or saving as PNG when JPEG or WebP would suffice. Compress your images to reduce file size without visible quality loss.