Recording Bitrate Calculator: Free Tool & Formula

This calculator works out the file size of a video or audio recording from its bitrate and duration, or the bitrate you need to hit a target file size. You enter the bitrate (in kbps or Mbps), the recording length, and optionally the number of audio and video streams; it returns the estimated file size in megabytes and gigabytes. It also works in reverse: enter a target file size and duration to find the required bitrate.

Formula

The core relationship is: File size = Bitrate × Duration. In practice, you must account for the difference between bits (used for bitrate) and bytes (used for file size), and between decimal (SI) and binary (IEC) units.

For a video with separate audio and video bitrates, the total bitrate is the sum:

Total bitrate (bps) = Video bitrate (bps) + Audio bitrate (bps)

Then, to get the file size in bytes:

File size (bytes) = Total bitrate (bps) × Duration (seconds) / 8

To convert to megabytes (MB, decimal): divide by 1,000,000. To convert to mebibytes (MiB, binary, often labelled MB by operating systems): divide by 1,048,576. The calculator above uses the binary definition for MB and GB because that matches what Windows and most file managers show.

Variables:

• Bitrate – the number of bits used per second of recording, in Mbps (megabits per second) or kbps (kilobits per second). 1 Mbps = 1,000 kbps.
• Duration – total recording time in seconds (hours × 3600 + minutes × 60 + seconds).
• File size – the resulting storage space, in MB or GB.

Worked Example

Using the default values: bitrate = 8 Mbps, duration = 1 hour (3600 seconds).

1. Convert bitrate to bits per second: 8 Mbps = 8,000,000 bps.
2. Multiply by duration: 8,000,000 × 3600 = 28,800,000,000 bits.
3. Divide by 8 to get bytes: 28,800,000,000 / 8 = 3,600,000,000 bytes.
4. Convert to MB (binary): 3,600,000,000 / 1,048,576 ≈ 3433.00 MB.
5. Convert to GB (binary): 3,600,000,000 / 1,073,741,824 ≈ 3.35 GB.

The calculator shows 3433.00 MB and 3.35 GB for the defaults.

Why Bitrate Matters in Recording

Bitrate is the single biggest factor in recording file size and quality. A higher bitrate preserves more detail (less compression artifacts) but produces larger files. Lower bitrates save space but can introduce visible blockiness or audio mush, especially in fast-moving scenes or complex audio.

Typical use cases:

• Screen recording: 1–8 Mbps for 1080p, depending on motion.
• Video calls: 1–2 Mbps for 720p, 2–4 Mbps for 1080p.
• Gameplay capture: 10–20 Mbps for 1080p60, 30–50 Mbps for 4K.
• Music recording: 256–320 kbps for MP3, 1411 kbps for CD-quality WAV.
• Podcast audio: 64–128 kbps for speech.

Most recording software (OBS Studio, Audacity, etc.) lets you set a bitrate or a “quality” slider that indirectly sets it. Knowing the resulting file size helps you plan storage and upload times.

How to Use the Calculator

You have two main workflows:

1. Estimate file size: Enter your recording bitrate (the total, or video+audio) and the duration. The calculator gives you the expected file size.
2. Find required bitrate: If you have a target file size (e.g., a 4 GB limit for a USB stick), divide the target size (in bits) by the duration (in seconds). The calculator does this in the third output line, but you need to enter a bitrate first – the third output shows the same bitrate you entered (since it’s derived from the same inputs). For a true reverse calculation, use the formula: Bitrate (Mbps) = (Target file size in MB × 8 × 1,048,576) / (Duration in seconds × 1,000,000).

For example, to fit a 2-hour movie on a 4.7 GB DVD: 4.7 GB ≈ 4,700 MB (decimal) or 4,480 MiB (binary). Using binary: 4,480 MB × 8 × 1,048,576 = 37,580,963,840 bits. Divide by 7200 seconds = 5.22 Mbps. That’s your total bitrate (video+audio).

Common Mistakes and Misconceptions

• Bits vs. bytes: Bitrate is in bits per second, file size is in bytes. Forgetting to divide by 8 gives a result 8× too large.
• Decimal vs. binary units: Hard drive manufacturers use decimal (1 GB = 1,000,000,000 bytes), while most operating systems show binary (1 GB = 1,073,741,824 bytes). A 100 GB drive shows as ~93.1 GB in Windows.
• Variable bitrate (VBR): The calculator assumes constant bitrate (CBR). VBR recordings are smaller because they use fewer bits for simple scenes, but the actual size varies. This calculator gives an upper bound for VBR.
• Container overhead: File size also includes metadata and container overhead (a few KB to a few MB), which is negligible for long recordings but can matter for short clips.
• Audio bitrate: For video, don’t forget to add the audio bitrate. A 10 Mbps video with 320 kbps audio is 10.32 Mbps total.

Choosing the Right Bitrate for Your Recording

There is no single “correct” bitrate – it depends on resolution, frame rate, content complexity, and your tolerance for quality loss. As a general guide:

• 1080p at 30 fps: 8–12 Mbps for high quality, 4–6 Mbps for acceptable quality.
• 1080p at 60 fps: 12–20 Mbps for high quality.
• 4K at 30 fps: 35–50 Mbps for high quality.
• 4K at 60 fps: 50–70 Mbps.
• Audio (music): 256–320 kbps for MP3, 500–1000 kbps for lossless formats like FLAC.

If you’re unsure, start with a medium bitrate and check the quality. For archival recordings, use a higher bitrate – you can always compress later, but you can’t recover detail that was lost.

Frequently Asked Questions

What is a good bitrate for screen recording?

For 1080p screen recording, 8–12 Mbps gives excellent quality for typical desktop use. If you’re recording fast-paced video or games, go higher (15–20 Mbps). For simple slideshows, 5 Mbps is often enough. Remember to add audio bitrate (usually 128–320 kbps).

Does a higher bitrate always mean better quality?

Up to a point, yes. Beyond a certain threshold, the encoder can’t improve quality further – you’re just wasting storage. The threshold depends on resolution and content. For 1080p, anything above ~20 Mbps is usually overkill for most content. For 4K, you might need 50+ Mbps to avoid artifacts in complex scenes.

Why does my recorded file size differ from the calculator?

Most likely because your recording uses variable bitrate (VBR), which adjusts bitrate based on content. Also, the calculator uses binary MB (1,048,576 bytes), while some software reports decimal MB (1,000,000 bytes). Container overhead and audio tracks add a tiny amount. Differences of 5–10% are normal.

How do I convert Mbps to MB per minute?

Divide the Mbps by 8 to get MB per second, then multiply by 60. For example, 10 Mbps = 1.25 MB/s = 75 MB/min. That’s a quick way to estimate storage needs without a calculator.

What bitrate should I use for recording music?

For MP3, 320 kbps is the highest quality setting. For lossless formats like FLAC, bitrate varies (typically 500–1000 kbps) because it’s not fixed. For speech/podcasts, 64–128 kbps is sufficient. Always record at a high bitrate and export to a lower one for distribution.

Can I use this calculator for live streaming?

Yes, but remember that streaming also requires your internet upload speed to be higher than the bitrate. For example, a 6 Mbps stream needs at least 7–8 Mbps upload. Also, streaming platforms often recommend specific bitrates (e.g., YouTube suggests 12 Mbps for 1080p60) – use those as a starting point.

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in bitrate | Bitrate | Mbps | 8 | 0
in hours | Hours | h | 1 | 0
in minutes | Minutes | min | 0 | 0
in seconds | Seconds | s | 0 | 0
out size_mb | File size | MB | (bitrate * 1000000 / 8) * (hours*3600 + minutes*60 + seconds) / 1048576 | 2
out size_gb | File size | GB | (bitrate * 1000000 / 8) * (hours*3600 + minutes*60 + seconds) / 1073741824 | 2
out bitrate_kbps | Required bitrate | kbps | ( (bitrate * 1000000) * (hours*3600 + minutes*60 + seconds) ) / ( (hours*3600 + minutes*60 + seconds) * 1000 ) | 2