Calculate how much data digital images, audio and video take up without compression. Change the resolution and color depth, or the sampling frequency and bit depth, to see how the size changes. Enter a compression ratio to estimate the compressed size and bit rate.
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Result
Size without compression
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Size after compression
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Bit rate (before → after compression)
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Time to send over the line (compressed)
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Sizes are shown with prefixes that step by 1000 (kB, MB, GB), with values stepping by 1024 (KiB, MiB, GiB) in parentheses. Real image and video files also contain headers and other extra information.
See it as a graph
Other inputs stay at their current values while the chosen input varies from 1/4 to 4 times its current value. The red dot is the current value.
Image data size
A digital image is recorded as an array of pixels. Its data size is horizontal pixels × vertical pixels × bits per pixel. Bits per pixel (color depth) is 24 for full color, which uses 8 bits each for red, green and blue and can show about 16.77 million colors. A full-color Full HD (1920 × 1080) image is about 6.2 MB without compression. As image sensors gain pixels, the data per image grows in proportion.
Audio data size: sampling and quantization
To digitize sound, the waveform is measured at regular intervals (sampling) and each value is rounded to one of a fixed number of levels (quantization). The data size is sampling frequency × quantization bits × channels × duration. A CD uses 44.1 kHz, 16 bits and stereo, which is 1411.2 kbit per second, or about 10.6 MB per minute. By the sampling theorem, sampling at more than twice the highest frequency in the original sound lets the waveform be reconstructed. CDs use 44.1 kHz to record up to about 20 kHz, the upper limit of human hearing.
Video data size and compression
Video shows many images per second, so its data size is the size of one frame × frame rate × duration. Uncompressed Full HD at 30 frames per second needs a bit rate of about 1.5 Gbps, about 11 GB per minute. Video is therefore stored and streamed after compression with codecs such as H.264 and H.265, which drop differences from neighboring frames and information the eye barely notices, reducing it to between a few tenths and a few hundredths of its size.
Relation to A/D converters
Sampling and quantizing audio is exactly what an A/D converter does when it turns an analog signal into digital form. Each extra quantization bit doubles the number of levels and improves the ideal signal-to-quantization-noise ratio by about 6 dB. Image sensors also use A/D converters to turn each pixel's brightness into a number, and the bits per pixel are set by that resolution.
Audio CDs store 44.1 kHz, 16-bit, two-channel audio at about 1.4 Mb/s. The rate slightly exceeds twice the ~20 kHz upper limit of hearing and is said to derive from figures convenient for recording on professional video equipment of the time. Sixteen bits give about 96 dB of dynamic range. Broadcasting and video use 48 kHz, high-resolution audio uses 96 or 192 kHz at 24 bits, and telephone speech uses 8 kHz.
The sampling theorem says a signal can be reconstructed if sampled faster than twice its highest frequency, so 20 kHz content requires more than 40 kHz. Since filters cannot cut off instantly, practical systems add margin: audio CDs sample at 44.1 kHz, using 20–22.05 kHz as the filter's transition band. Half the sampling frequency is called the Nyquist frequency.
FAQ
What improves when I increase the quantization bits?
Each sample can be represented in finer steps, so the error from the original waveform (quantization noise) gets smaller. Each extra bit doubles the number of levels, and the data size grows in proportion to the number of bits.
How many bits per pixel does a 256-color image use?
256 = 2⁸, so 8 bits. Two colors need 1 bit, 65,536 colors need 16 bits and about 16.77 million colors (full color) need 24 bits.
What does a compression ratio of 1/100 mean?
The compressed data is one hundredth of the original size. In this tool, enter the N in 1/N (here, 100) as the compression ratio.
How does this appear on exams?
IT certification exams such as Japan's Fundamental Information Technology Engineer Examination often ask for the storage needed for an image from its resolution and number of colors, the size of audio from its sampling frequency and quantization bits, or the bit rate needed to send video over a line.