Image File Size Calculator
Work out how large an image will be before you create it. Enter the width, height and colour depth to get the exact uncompressed and BMP sizes, the megapixels and the print size at your resolution, plus typical sizes for JPG, WebP, AVIF and PNG. For exact compressed sizes, measure your own image: it is encoded in several formats and qualities right in your browser.
- Runs in your browser
- No sign-up
- Free to use
Used for the print size.
Uncompressed and BMP sizes are exact. Compressed sizes are typical ranges – the real size depends on the image content. Test your own image below for exact numbers.
Measure your own image
Choose an image to see the exact file size it gets in each format and quality, encoded in your browser.
How to use Image File Size Calculator
- Enter width and height in pixels.
- Choose the colour depth and whether it is a photo or a graphic.
- Read the exact and typical sizes.
- Optionally measure an image of your own.
Image File Size Calculator features
Exact raw sizes
Uncompressed and BMP, with the formula.
Typical compressed sizes
JPG, WebP, AVIF, PNG ranges.
Megapixels
And aspect information.
Print size
Centimetres and inches at any dpi.
Real measurement
Encode your image to see actual sizes.
Private
Converted in your browser; nothing is uploaded.
When to use Image File Size Calculator
- Estimating storage for photo archives and scans.
- Planning image budgets for websites.
- Checking camera and scanner settings.
- Understanding why some files are so large.
Image File Size Calculator FAQ
How is the uncompressed size calculated?
Width × height × bits per pixel ÷ 8. A 4000 × 3000 photo at 24 bits needs 36,000,000 bytes, about 34.3 MB, in memory.
Why are the compressed sizes ranges?
Compression depends on the content: a smooth sky compresses far better than leaves or noise. The ranges show typical results; measuring your own image gives exact numbers.
What is bits per pixel?
The average number of bits a compressed file uses for each pixel. JPG photos are often 1–3 bits per pixel, compared with 24 uncompressed.
How is the print size calculated?
Pixels ÷ dots per inch. 3000 pixels at 300 dpi print 10 inches, or 25.4 cm, wide.
Is my image uploaded when I measure it?
No. It is encoded in your browser.
What determines image file size
An image is a grid of pixels, and each pixel needs a certain number of bits: 1 for pure black and white, 8 for greyscale or a palette of 256 colours, 24 for full colour, 32 with transparency, and 48 or 64 for the 16-bit-per-channel images of RAW and professional TIFF files. Multiplying the pixel count by the bits per pixel gives the uncompressed size, which is what the image occupies in memory and in an uncompressed BMP.
File formats then compress that data. Lossless formats like PNG find patterns and repetitions; they work very well on screenshots and graphics but only modestly on photos. Lossy formats like JPG, WebP and AVIF discard detail the eye barely notices and reach a small fraction of the raw size: typical photos need 1 to 3 bits per pixel as JPG and less as WebP and AVIF.
Because compression depends on the content, typical ranges are the best any calculator can honestly give without the image itself. That is why the tool also measures real files: choose an image and it is encoded as JPG and WebP at several qualities and as PNG, showing actual sizes and bits per pixel.
Print size depends only on pixels and resolution. At 300 dpi, the usual quality for photo prints, each inch needs 300 pixels; at 150 dpi, posters viewed from a distance still look good.
All calculations and measurements happen in your browser.