Retina Image Size Calculator

Work out @1x, @2x and @3x pixel dimensions from one base size, and estimate the uncompressed size of each image. Useful when preparing assets for iOS, Android and high-DPI web displays.

Base width (points or CSS pixels) Base height (points or CSS pixels) Bits per pixel (uncompressed)

How to use

Enter the base size in points (iOS) or CSS pixels (web/Android density-independent pixels).
Choose the colour depth that matches your image type.
Press Calculate to see dimensions and raw size for each scale.

How it works

Retina scales multiply each dimension: @2x doubles width and height, @3x triples them. The uncompressed size is width × height × bits per pixel ÷ 8, shown in bytes before compression. PNG and JPEG files are usually much smaller because they compress data.

When to use this calculator

Exporting app icons, logos, buttons or UI images for iPhone, iPad, Android or the web.
Planning memory use for a game or app that loads many textures.
Checking that a 1x asset will not look blurry when displayed on a high-density screen.
Estimating the raw size of image data before compression.

Worked examples

200 × 200 base size: @2x is 400 × 400 px and @3x is 600 × 600 px - the standard iOS asset set.
1024 × 1024 app icon: @2x would be 2048 × 2048 px; app stores usually want the 1024 px base version.
400 × 300 RGBA image at @2x: 800 × 600 px, about 1.83 MB of uncompressed texture data per frame at 32 bits per pixel.
Web hero image 1200 × 600 CSS px: export at 2400 × 1200 px for @2x screens.

Base size, scale factor and device pixels

Design tools work in points or CSS pixels, while screens are made of physical device pixels. A modern phone with a device pixel ratio of 3 uses nine physical pixels for every CSS pixel. Exporting at the matching scale keeps edges sharp without shipping unnecessarily huge files; exporting at 4x "just in case" multiplies both file size and memory use.

Uncompressed size vs file size

The size estimate shows raw pixel data, which is what matters for GPU memory and uncompressed formats such as BMP or TIFF. PNG and JPEG files on disk are smaller because they compress data. A texture that is 4 MB uncompressed might be a 400 KB PNG - useful to know when planning download size versus runtime memory.

Common mistakes

Exporting only @2x and relying on browsers to upscale for @3x screens.
Using the same file name for all scales and accidentally shipping the 1x version.
Confusing points with pixels when the design tool already works in device pixels.
Assuming a larger scale always improves quality - beyond the screen's density it only adds weight.

Frequently asked questions

Why do my exported PNG files not match this size estimate?

Because PNG applies lossless compression and JPEG applies lossy compression. The estimate shows the raw pixel data size (like an uncompressed BMP or an in-memory texture), which is useful for memory planning, not file-size planning.

What resolution do I need for Retina web images?

Export the image at @2x (or @3x for very high-density phones) and display it at CSS-pixel size. Browsers downscale automatically, which keeps the image sharp.