Calculate how much storage bitmap images and sound files need โ with full working shown step by step.
Designed with the WJEC specification in mindResolution = width ร height (total number of pixels)
Colour depth = number of bits per pixel. More bits = more colours but bigger file.
Formula: File size = width ร height ร colour depth
This gives the uncompressed file size. Real images (JPEG, PNG) use compression to reduce this.
Sample rate = how many times per second the sound wave is measured (Hz).
Bit depth = how many bits are used to store each sample. More bits = more detail.
Channels = mono (1) or stereo (2). Stereo doubles the file size.
Formula: File size = sample rate ร bit depth ร channels ร duration
Audio track:
FPS (Frames Per Second) = how many still images are shown each second. Higher FPS = smoother motion but bigger files.
Video formula: File size = (width ร height ร colour depth ร FPS ร duration) + audio size
A video is just a sequence of bitmap images played quickly, plus an audio track. That's why uncompressed video is enormous โ a 2-minute 1080p clip is about 22 GB uncompressed!
Real video files (MP4, MKV) use lossy compression to shrink this by 100-1000ร. That's why compression is so important.
| Unit | Size | Real-world example |
|---|---|---|
| 1 Bit | 0 or 1 | A single yes/no answer |
| 1 Byte (B) | 8 bits | One character (letter, number, symbol) |
| 1 Kilobyte (KB) | 1,024 bytes | A short text message or email |
| 1 Megabyte (MB) | 1,024 KB | A photo from your phone, or a 1-minute MP3 |
| 1 Gigabyte (GB) | 1,024 MB | About 250 songs, or a 1-hour Netflix show (compressed) |
| 1 Terabyte (TB) | 1,024 GB | About 500 hours of HD video, or a laptop hard drive |
| 1 Petabyte (PB) | 1,024 TB | All the photos on Facebook, or Netflix's entire library |
| 1 Exabyte (EB) | 1,024 PB | All the data on the internet is roughly 5 exabytes |
See how different settings affect file size. Click a scenario to see the working.