Bitrate Calculator
Calculate file size, bitrate, or duration from any two of the three. Includes presets for YouTube, Netflix, Spotify, and Blu-ray.
About Bitrate Calculator
Bitrate, file size, and duration are linked: if you know any two, you can calculate the third. This calculator works in all three directions - find file size from bitrate and duration, find bitrate from file size and duration, or find duration from file size and bitrate. Built-in presets for common media formats speed up the calculation. All processing runs in your browser.
The Three Calculation Modes
| Mode | You Know | You Get | Use Case |
|---|---|---|---|
| Bitrate + Duration → File Size | Bitrate (e.g., 25 Mbps) and duration (e.g., 2 hours) | Estimated file size | Planning storage for a recording session |
| File Size + Duration → Bitrate | Target file size (e.g., 4.7 GB) and duration (e.g., 2 hours) | Required bitrate | Encoding to fit a specific storage limit |
| File Size + Bitrate → Duration | File size and known bitrate | Playback duration | Estimating how long a media file will play |
The formula: File Size (bits) = Bitrate (bits/sec) x Duration (seconds). Divide by 8 to convert bits to bytes.
Common Bitrate Presets
| Format / Service | Bitrate | 1 Hour File Size | Quality |
|---|---|---|---|
| Spotify Normal | 96 kbps | ~43 MB | Acceptable for speech, lossy music |
| Spotify High Quality | 320 kbps | ~144 MB | Good quality compressed audio |
| CD Audio (uncompressed) | 1,411 kbps | ~635 MB | Lossless stereo audio |
| YouTube 1080p | ~8 Mbps | ~3.6 GB | Standard HD streaming |
| YouTube 4K | ~20 Mbps | ~9 GB | Ultra HD streaming |
| Netflix HD | ~5 Mbps | ~2.25 GB | 1080p streaming (adaptive) |
| Netflix 4K HDR | ~15-25 Mbps | ~6.75-11.25 GB | 4K with HDR (adaptive) |
| Blu-ray | ~25-40 Mbps | ~11.25-18 GB | Full quality 1080p disc |
| 4K Blu-ray (UHD) | ~50-100 Mbps | ~22.5-45 GB | Full quality 4K disc |
Bits vs Bytes
Bitrate is measured in bits per second (bps), but file sizes are measured in bytes. There are 8 bits in a byte. This distinction matters:
| Unit | Symbol | Used For |
|---|---|---|
| Kilobits per second | kbps | Audio bitrates (128 kbps, 320 kbps) |
| Megabits per second | Mbps | Video bitrates, network speeds |
| Megabytes | MB | File sizes |
| Gigabytes | GB | Larger file sizes, storage capacity |
A 10 Mbps video stream uses 10/8 = 1.25 MB per second, or 4.5 GB per hour.
Variable vs Constant Bitrate
| Type | How It Works | File Size | Quality |
|---|---|---|---|
| CBR (Constant Bitrate) | Same bitrate every second | Predictable (this calculator assumes CBR) | Wastes bits on simple scenes, may lack bits for complex ones |
| VBR (Variable Bitrate) | Adjusts bitrate based on content complexity | Varies - typically smaller than CBR at same quality | Better quality per bit - more bits for complex scenes |
| ABR (Average Bitrate) | Targets an average but varies moment to moment | Close to predicted but not exact | Compromise between predictable size and VBR quality |
Real-world video files almost always use VBR or ABR, so actual file sizes may be 5-15% different from the CBR estimate this calculator produces.
To estimate how long a file takes to transfer over a network, the file transfer time calculator supports all common connection types. For converting between storage units, the storage converter handles bytes, KB, MB, GB, and TB. All calculations run in your browser.
Frequently Asked Questions
What is bitrate?
Bitrate is the amount of data processed per second in a media stream. It is measured in bits per second (bps). Higher bitrates generally mean better quality for audio and video, but also larger file sizes.
How do I estimate the size of a video recording?
Multiply the bitrate by the duration. For example, a 2-hour video at 8 Mbps uses roughly 7.2 GB. This calculator handles the maths for you across different units.
What bitrate should I use for YouTube uploads?
YouTube recommends about 8 Mbps for 1080p at 30fps and 35-45 Mbps for 4K at 30fps. Higher frame rates need roughly 50% more bitrate. These are guidelines - YouTube re-encodes everything after upload.
Why does the calculated file size differ from my actual file?
Real files include container overhead, metadata, variable bitrate encoding, and multiple tracks (audio, subtitles). The calculator gives a close estimate based on a constant bitrate, which works well for planning storage and bandwidth.
What is the difference between kbps and Mbps?
kbps (kilobits per second) and Mbps (megabits per second) differ by a factor of 1,000. Audio is usually measured in kbps (128-320 kbps), while video uses Mbps (5-50 Mbps). Both use bits, not bytes.
Related Tools
Link to this tool
Copy this HTML to link to this tool from your website or blog.
<a href="https://toolboxkit.io/tools/bitrate-calculator/" title="Bitrate Calculator - Free Online Tool">Try Bitrate Calculator on ToolboxKit.io</a>