Video File Size Calculator

Calculate video file size from bitrate and duration, or estimate the bitrate needed for a target file size. Essential for storage planning and upload preparation.

Calculation Mode

Duration

Hours

Minutes

Seconds

Video Quality Preset

Audio Bitrate (kbps)

About Video File Size Calculator

Understanding Video File Size

Video file size is determined by the bitrate (data rate) of the video and audio streams multiplied by the duration of the recording. Understanding this relationship is essential for anyone working with video — whether you are a content creator planning storage needs, a videographer preparing for a long shoot, or simply trying to figure out if your file will fit on a USB drive or upload within a reasonable time.

The fundamental formula is straightforward: File Size = (Video Bitrate + Audio Bitrate) × Duration. The video bitrate is typically measured in megabits per second (Mbps), while audio bitrate is measured in kilobits per second (kbps). When you know any two of the three variables — file size, bitrate, and duration — you can calculate the third.

Key Concepts:

Bitrate: The amount of data processed per second of video
CBR: Constant bitrate — same data rate throughout the video
VBR: Variable bitrate — data rate adapts to scene complexity
Codec: The compression algorithm (H.264, H.265, AV1, ProRes)
Container: The file format (MP4, MOV, MKV, AVI)

Video Bitrate and Quality Settings

Choosing the right bitrate is a balancing act between file size and visual quality. Higher bitrates produce better-looking video but generate larger files. The resolution and frame rate of your video are the primary factors that determine how much bitrate you need for acceptable quality.

Recommended Bitrates

Resolution	Bitrate
720p 30fps	5 Mbps
1080p 30fps	8 Mbps
1080p 60fps	12 Mbps
4K 30fps	35 Mbps
4K 60fps	53 Mbps

Codec Efficiency

Codec	Efficiency
H.264 / AVC	Baseline (1×)
H.265 / HEVC	~50% smaller
AV1	~50-60% smaller
ProRes 422	~5× larger

Modern codecs like H.265 (HEVC) and AV1 achieve significantly better compression than the older but widely compatible H.264 codec. This means you can use lower bitrates with newer codecs and still maintain excellent visual quality, resulting in smaller files. Professional production codecs like ProRes prioritize editing performance over compression, producing much larger files.

Storage Planning and Upload Considerations

Accurate file size estimation is crucial for practical video production planning. Whether you are preparing memory cards for a wedding shoot, calculating how many hours of security footage your hard drive can hold, or estimating upload times for YouTube, knowing your expected file sizes prevents unpleasant surprises.

For storage planning, always add a 10-15% buffer above your estimates. Variable bitrate encoding means complex scenes (action, confetti, foliage) will produce larger files than static scenes. Also account for multiple takes, B-roll footage, and any post-production proxies or renders you may need to store.

Quick Storage Estimates (1 Hour):

720p 30fps (~5 Mbps): approximately 2.25 GB per hour
1080p 30fps (~8 Mbps): approximately 3.6 GB per hour
1080p 60fps (~12 Mbps): approximately 5.4 GB per hour
4K 30fps (~35 Mbps): approximately 15.75 GB per hour
4K 60fps (~53 Mbps): approximately 23.85 GB per hour

Audio Bitrate and Its Impact

While video bitrate dominates overall file size, audio bitrate also contributes — especially for longer recordings. Standard audio bitrates range from 128 kbps for acceptable quality to 320 kbps for high-quality stereo audio. Professional productions may use uncompressed audio (PCM) at bitrates of 1,536 kbps or higher for 48kHz 16-bit stereo.

For most video projects, 256-320 kbps AAC or 320 kbps MP3 audio provides excellent quality. At 320 kbps, one hour of audio adds approximately 144 MB to your total file size. While this seems small compared to video, it adds up over long recording sessions and should be factored into your storage calculations.

Multi-channel audio (5.1 surround, Dolby Atmos) requires proportionally higher bitrates. A 5.1 surround track at high quality might use 640 kbps to 1.5 Mbps, significantly increasing the audio contribution to your total file size, particularly for film and broadcast productions.

Frequently Asked Questions

How is video file size calculated?

Video file size is calculated by multiplying the total bitrate (video bitrate plus audio bitrate) by the duration. The formula is: File Size = (Video Bitrate + Audio Bitrate) × Duration. For example, a 10-minute video at 8 Mbps video bitrate and 320 kbps audio would be approximately 625 MB.

What bitrate should I use for 4K video?

For 4K video at 30fps, a bitrate of around 35 Mbps is typical for high-quality recording. At 60fps, expect to need around 53 Mbps or higher. YouTube recommends 35-45 Mbps for 4K SDR uploads and 44-56 Mbps for 4K HDR. Professional workflows may use even higher bitrates for maximum quality.

Why is my video file larger than the calculator estimated?

Variable bitrate (VBR) encoding, which most modern codecs use, can cause actual file sizes to differ from estimates. Complex scenes with lots of motion require more data than static scenes. The calculator uses constant bitrate (CBR) assumptions, so VBR-encoded videos may be slightly larger or smaller depending on content complexity.

How much storage do I need for a full day of recording?

Storage needs depend on your recording settings. At 1080p 30fps (~8 Mbps), one hour uses roughly 3.6 GB, so a full 8-hour day would need about 29 GB. At 4K 30fps (~35 Mbps), one hour uses about 15.75 GB, meaning 8 hours would require approximately 126 GB. Always plan for extra headroom beyond your estimates.

What is the difference between video bitrate and audio bitrate?

Video bitrate determines the quality and data rate of the visual component, typically measured in Mbps (megabits per second). Audio bitrate controls the quality of the sound track, usually measured in kbps (kilobits per second). Audio bitrate is much lower than video — typically 128-320 kbps — and contributes only a small fraction of the total file size.

How do I reduce video file size without losing quality?

Use a modern codec like H.265/HEVC or AV1, which can achieve the same visual quality at roughly half the bitrate of H.264. You can also reduce resolution or frame rate if the content allows it, use variable bitrate encoding, and trim unnecessary footage. Two-pass encoding also helps optimize quality-to-size ratios.

Additional Resources

Bitrate - Wikipedia Video Codec - Wikipedia

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