Image File Size Calculator
Estimate an uncompressed image's size from its dimensions.
24 for standard color, 32 with an alpha channel.
Results update as you type.
How it works
An image file size calculator estimates how much space an uncompressed image occupies from three numbers: its width and height in pixels and its bit depth, the number of bits used to describe each pixel's colour. Because a raw bitmap stores a fixed amount of data per pixel, this gives a precise upper bound on size, which is exactly what formats like BMP or uncompressed TIFF produce and what a program holds in memory while editing. The estimate helps when planning storage, memory use, and bandwidth. A photographer batching thousands of raw frames, a developer sizing a texture budget, or anyone deciding whether images fit a card or upload limit needs to know the worst-case footprint before compression. It also reveals how quickly dimensions inflate size: doubling both width and height quadruples the pixel count and the file. The formula works by counting total bits as pixels multiplied by bit depth, then converting to bytes by dividing by eight and to megabytes by dividing by 1,048,576. Common bit depths are 24 bits for full colour and 32 bits when an alpha transparency channel is added. Real saved files are usually far smaller because formats like JPEG and PNG compress the data, so treat this as the uncompressed maximum. Designers, photographers, and developers use an image size calculator to plan storage and memory around raw image data.
size (MB) = width × height × bit depth ÷ 8 ÷ 1,048,576
An uncompressed image stores a fixed number of bits for every pixel, so the total bits equal the pixel count, width times height, multiplied by the bit depth. Dividing by eight converts bits to bytes, and dividing by 1,048,576 (1,024 squared) converts bytes to megabytes. The method works because a raw bitmap has no compression, so its size is exactly the sum of the bits it dedicates to each of its pixels.
Source:Standard digital media
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter width, height and bit depth.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
File size updates instantly as you type — no button to press.
Frequently asked questions
Why is my saved image much smaller than this?
This calculator estimates the uncompressed size, the raw data with no compression applied. Real formats like JPEG, PNG, and WebP compress images significantly, often shrinking them to a fraction of the raw figure. JPEG in particular can reduce a photo by ten times or more with little visible loss. The uncompressed number is useful for memory planning and worst-case storage, while the saved file reflects the compression your format applies.
What bit depth should I use?
Standard full-colour images use 24 bits per pixel, eight bits each for red, green, and blue. Add an alpha transparency channel and it becomes 32 bits. High dynamic range or professional workflows may use 48 bits or more for finer gradation. Grayscale images use 8 bits. Choose the depth that matches your image: 24 is right for most colour photos, and 32 when you need transparency.
How does resolution affect file size?
File size scales with the total pixel count, which is width times height. Because both dimensions multiply, doubling each one quadruples the pixels and therefore the size. A 4K image has four times the pixels of a 1080p image and roughly four times the raw size. This quadratic growth is why high-resolution images consume storage and memory so quickly, and why resizing is such an effective way to save space.
Does this apply to images in memory too?
Yes, and that is one of its most useful applications. When a program opens an image to edit or display it, the image is typically held uncompressed in memory at roughly this size, regardless of how small the compressed file on disk is. This is why editing many large images can exhaust memory even when the saved files seem modest. The calculator estimates that in-memory footprint accurately.
Why divide by 1,048,576 for megabytes?
In computing, a megabyte is often defined as 1,024 kilobytes, and a kilobyte as 1,024 bytes, so one megabyte equals 1,024 times 1,024, which is 1,048,576 bytes. This calculator uses that binary convention. Some storage manufacturers instead use 1,000,000 bytes per megabyte, which is why advertised drive capacities can look slightly larger than what an operating system reports for the same space.