Video File Size Calculator
Calculate video file size from bitrate and duration, or estimate the bitrate needed for a target file size. Useful for storage planning and upload preparation.
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 useful 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.
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.
| Resolution | Bitrate |
|---|---|
| 720p 30fps | 5 Mbps |
| 1080p 30fps | 8 Mbps |
| 1080p 60fps | 12 Mbps |
| 4K 30fps | 35 Mbps |
| 4K 60fps | 53 Mbps |
| 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 noticeably 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.
Accurate file size estimation is important 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.
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.
Two files with the same resolution and duration can have very different sizes because bitrate is a choice, not a fixed property of the picture. A talking-head interview with a steady background can be compressed efficiently. A sports clip with camera movement, crowd detail, confetti, and fast cuts needs more data to avoid blockiness and smearing.
Variable bitrate encoding makes this harder to predict. The encoder spends fewer bits on simple scenes and more bits on complex ones, so the final file may land above or below a rough estimate. Constant bitrate is easier to calculate, but it may waste data on simple scenes or starve difficult ones. For planning memory cards, treat the calculator result as a baseline and leave extra space.
Codec settings also matter. H.265 and AV1 can often deliver similar quality at a lower bitrate than H.264, but compatibility may be worse on older devices. Production codecs such as ProRes or DNxHR create large files on purpose because they are easier to edit and grade.
Storage planning is more practical when you calculate by the longest likely recording day, not by the final edited video. A one-hour final cut may come from five or ten hours of source footage. Multi-camera shoots multiply that quickly. If each camera records 4K at 100 Mbps, three cameras running for four hours can fill hundreds of gigabytes before backups or proxies are created.
Upload planning has a different bottleneck. Internet providers often advertise download speed, while upload speed is much lower. A 20 GB file on a 20 Mbps upload connection takes more than two hours under ideal conditions, and real networks add overhead, throttling, and interruptions. Smaller proxy files or a lower delivery bitrate can save a lot of time when a client only needs review access.
Video bitrates are usually written in bits per second, while storage devices are sold in bytes. There are 8 bits in 1 byte, so a 40 Mbps video stream uses about 5 MB per second before container overhead. That small distinction explains many file-size surprises.
Decimal and binary units can add another mismatch. Drive makers use decimal gigabytes, where 1 GB is 1,000,000,000 bytes. Some operating systems report gibibytes, where 1 GiB is 1,073,741,824 bytes. The drive did not shrink; the labels are using different counting systems.
A file meant for viewers is usually compressed for efficient playback. A file meant for editing is often larger because it preserves more image information and is easier for software to scrub, cut, and color correct. Confusing those two goals leads to either bloated uploads or fragile editing files that fall apart after color grading.
For a final upload, choose settings based on the platform, resolution, frame rate, and how much detail the footage contains. For editing, consider an intermediate codec or proxy workflow. Proxies are smaller working copies that make editing smoother while the final export still uses the full-quality source files.
Archiving is a third case. You may want to keep camera originals, project files, audio stems, captions, thumbnails, and the final master. The calculator can estimate each video file, but a real archive also needs folder structure, checksums or verification, and at least one backup stored away from the main drive.
Frame rate changes size because it changes how many pictures are stored each second. A 60 fps export usually needs more bitrate than a 30 fps export at the same resolution. Grain, noise, screen recordings, text, and fast camera movement can also demand more bits than clean, static footage.
Audio rarely dominates a modern video file, but it still matters for podcasts, lectures, concerts, and long recordings. Multi-track audio, surround mixes, or uncompressed WAV tracks can add gigabytes over a long project. Include them when planning storage instead of treating audio as free.
A good storage estimate includes a buffer. For controlled studio recording with constant bitrate, 10% may be enough. For variable bitrate footage, live events, weddings, sports, wildlife, or anything that cannot be reshot, 25% to 50% extra space is safer. Running out of card space during the final minutes of an event is far worse than carrying an extra card home unused.
Backups need the same math. One copy on the camera card is not a backup. A common field workflow is card, working drive, and backup drive before formatting anything. Larger files also take longer to copy, verify, and upload, so storage planning should include time as well as capacity.
If the estimate looks too large, lower bitrate first only if quality still meets the delivery need. Dropping resolution or frame rate can save more space, but it changes the creative result. A better codec may reduce size without changing the look, as long as the editor and viewers can play it reliably.
Imagine two cameras recording 4K at 100 Mbps for a three-hour event. One camera at 100 Mbps uses about 45 GB per hour, so two cameras use about 270 GB for the event before audio backups, extra takes, or proxies. Add a 25% buffer and the working total is closer to 340 GB.
That estimate changes the gear list. A single small card may not be enough, and the copy time after the shoot becomes part of the job. If the final delivery is only a 12 GB web file, that does not reduce the source storage needed during production. Source, edit, archive, and delivery files each need their own estimate.
The bitrate formula gives the main file size, but containers add a little overhead for indexes, metadata, timecode, subtitles, chapters, and audio track information. For most MP4 or MOV exports this overhead is small, but it explains why a real file may not match the calculated value byte for byte.
Some workflows also create sidecar files: captions, LUTs, project files, waveform caches, preview renders, and thumbnails. They may be small compared with camera originals, but they matter when packaging a project for handoff or long-term storage.
When estimating many files, round up each file rather than only the grand total. Small overhead and rounding differences add up across a day of clips, especially when cameras split long recordings into many separate files.
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.
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.
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.
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.
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.
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.
Embed on Your Website
Add this calculator to your website