How big will my video file be?

Multiply your video bitrate plus audio bitrate (in Mbps) by the duration in seconds, then divide by 8 to get megabytes. An 8 Mbps 1080p video with 128 kbps audio for 10 minutes comes out to roughly 610 MB.

Video Bitrate & File Size Calculator

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Walk-through

How to Use This Calculator

5 steps

1

Pick a mode

Choose File Size to calculate size from a bitrate you already know, Target Size Solver to work backward from a size limit (like a 500 MB upload cap), or Platform Presets to get a recommended bitrate for YouTube, Twitch, Instagram, or TikTok.

2

Set resolution, frame rate, and duration

These live in the Video Settings card and apply across every mode — pick your resolution, frame rate, and the length of your video in minutes. Higher frame rates need more bitrate for the same visual quality.

3

Enter your bitrate, target size, or platform

On File Size, enter the video bitrate in Mbps. On Target Size Solver, enter the file size you're aiming for in MB. On Platform Presets, pick the platform and context (like YouTube 4K SDR or Twitch/OBS streaming).

4

Read the result

The result card shows the file size, the required bitrate, or the recommended bitrate depending on your mode — plus a breakdown of video size, audio size, and total size.

5

Compare codecs

Switch the Codec setting between H.264, H.265, and AV1 to see how much smaller the same-quality file gets with a more efficient codec — the comparison table and chart update to show all three side by side.

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Reference

Formula & Methodology

3 formulas

File size from bitrate and duration

size (MB) = ((video Mbps + audio Mbps) × duration in seconds) ÷ 8

Bitrate is measured in megabits per second; dividing the total bits by 8 converts to megabytes. Audio bitrate (typically 128-384 kbps) is converted to Mbps and added to the video bitrate before this calculation.

Target size to required bitrate

required video Mbps = (target size MB × 8 ÷ duration in seconds) − audio Mbps

This inverts the size formula to solve for the video bitrate that hits a specific file size, after subtracting out the audio track's share. If the target size is too small for the duration and audio alone, the required bitrate clamps to zero.

Codec efficiency comparison

equivalent bitrate = (entered bitrate ÷ codec multiplier) × target codec multiplier

H.265 typically needs about half the bitrate of H.264 for the same visual quality (multiplier 0.5), and AV1 needs roughly 30-50% less than H.265 (multiplier ~0.4). The calculator normalizes your entered bitrate to an H.264-equivalent baseline, then scales it to each codec to show what the same quality would cost in bitrate and file size.

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Glossary

Key Terms Explained

9 terms

Bitrate The amount of data used per second of video or audio, usually measured in megabits per second (Mbps) for video and kilobits per second (kbps) for audio. Higher bitrate generally means better quality and a larger file.

CBR vs. VBR Constant bitrate (CBR) keeps the bitrate fixed throughout the video, making file size predictable — the standard choice for live streaming. Variable bitrate (VBR) adjusts bitrate scene by scene, using more data for complex motion and less for static scenes, usually producing a smaller file at the same average quality.

Resolution The pixel dimensions of the video (e.g., 1920×1080 for 1080p, 3840×2160 for 4K). Higher resolution needs more bitrate to maintain the same visual quality, since there are more pixels to encode per frame.

Frame rate How many frames of video are shown per second (fps). Common values are 24-30fps for standard video and 48-60fps for smooth motion or gaming. Higher frame rates need more bitrate because there's more motion data to encode each second.

Codec The compression algorithm used to encode video, such as H.264, H.265, or AV1. Different codecs achieve different levels of compression efficiency — a more efficient codec produces a smaller file at the same visual quality, at the cost of slower encoding.

H.264 / H.265 / AV1 H.264 (AVC) is the most widely compatible codec, playable on nearly every device. H.265 (HEVC) roughly halves the bitrate needed for the same quality but has more limited hardware support. AV1 is the newest and most efficient, needing even less bitrate, but encodes slower and has the least universal playback support.

Container The file format that wraps the encoded video and audio streams together, such as MP4, MOV, or MKV. The container doesn't affect the bitrate math — it's the codec inside that determines compression efficiency.

SDR / HDR Standard Dynamic Range (SDR) is the traditional color and brightness range most video is shot and viewed in. High Dynamic Range (HDR) carries a wider range of brightness and color, producing more realistic images but requiring roughly 40-50% more bitrate at the same resolution to avoid visible compression artifacts.

Encode speed How quickly a codec can compress video, often measured in frames processed per second during export. More efficient codecs (H.265, AV1) generally encode much slower than H.264 for the same source video, which matters for time-sensitive exports.

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Scenarios

Real-World Examples

3 worked examples

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YouTube creator exporting a 1080p video

File Size mode — checking upload size before exporting

Resolution 1080p Video bitrate 8 Mbps Audio bitrate 128 kbps Duration 10 min

At 8 Mbps video plus 128 kbps audio for 10 minutes, the file comes out to about 610 MB — comfortably within most upload limits, and right in line with YouTube's own 1080p SDR recommendation.

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Uploader with a 500 MB size cap

Target Size Solver mode — a Discord or email attachment limit

Target file size 500 MB Duration 10 min Audio bitrate 128 kbps

To land at 500 MB over a 10-minute video, encode at roughly 6.5 Mbps video bitrate — noticeably below the default 8 Mbps, so expect a small quality trade-off at 1080p.

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Someone deciding between codecs

Codec comparison — same visual quality, smaller file

Video bitrate (H.264) 8 Mbps Codec H.264 → H.265 Duration 10 min

That same 8 Mbps H.264 video, re-encoded in H.265 at equivalent visual quality, needs only about 4 Mbps — bringing the file down from roughly 610 MB to about 310 MB, at the cost of slower encoding and slightly narrower device compatibility.

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Deep Dive

One Tool for the Whole Video File-Size Question

4 chapters · 5 min read

"How big will this export be?", "what bitrate do I need to hit a 500 MB cap?", and "what does YouTube actually want for 4K?" are three versions of the same underlying math, but they usually send you to three different places — a vague forum thread, a manual calculation, or a platform help page. This calculator answers all three from one set of inputs, plus the codec-efficiency question (H.264 vs. H.265 vs. AV1) that's normally left out entirely.

File size is just bitrate times time

Every video file's size comes down to one relationship: how much data is used per second (bitrate), multiplied by how many seconds the video runs. Add the audio track's bitrate to the video's, multiply by duration, and divide by 8 to convert bits to bytes — and you have the file size. The math is simple, but doing it by hand for every resolution, frame rate, and codec combination gets tedious fast, which is why this calculator exists.

Working backward from a size limit

Upload caps are everywhere — a 500 MB email attachment limit, a Discord free-tier cap, a client's FTP quota — and the natural question flips from "how big will this be" to "what bitrate keeps me under the limit." The Target Size Solver inverts the same formula to answer that directly, so you can set your export bitrate before you render instead of finding out you're over the limit after.

Platforms all want something slightly different

YouTube, Twitch, Instagram, and TikTok each publish their own recommended upload or streaming bitrates, and they're not the same — YouTube's 4K guidance alone varies by SDR vs. HDR and by frame rate, while Twitch caps most streamers around 6 Mbps regardless of resolution. The Platform Presets tab collects the current guidance for the platforms creators actually use, so you don't have to dig through each platform's help center separately. These figures are approximate and platforms do revise them occasionally, so treat them as a strong starting point rather than a guarantee.

The codec question nobody puts a number on

Everyone's heard that H.265 files are "smaller" than H.264, and that AV1 is smaller still, but rarely with an actual number attached. At equivalent visual quality, H.265 typically needs about half the bitrate of H.264, and AV1 needs another 30-50% less than that — which is exactly what the codec comparison table and chart show for your specific bitrate and duration, so the trade-off (smaller file vs. slower encode and narrower compatibility) is a real number, not a rule of thumb.

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Questions

Frequently Asked Questions

8 questions

How do I calculate video file size from bitrate?+

Add your video bitrate and audio bitrate together (converting to the same unit, Mbps), multiply by the duration in seconds, then divide by 8 to convert bits to bytes. An 8 Mbps 1080p video with 128 kbps audio over 10 minutes comes out to about 610 MB.

What's the best bitrate for 4K YouTube?+

YouTube recommends roughly 45 Mbps for 4K (2160p) SDR at 24-30fps, and around 68 Mbps at 48-60fps — higher still for HDR. Use the Platform Presets tab for the exact recommendation matching your resolution, frame rate, and SDR/HDR choice.

What bitrate should I use for OBS and Twitch?+

Twitch's standard guidance caps most streamers at about 6 Mbps video bitrate, which is what the Platform Presets tab uses as the default OBS/Twitch recommendation. Streamers enrolled in Twitch's Enhanced Broadcasting program can go higher.

How much smaller is H.265 than H.264?+

At the same visual quality, H.265 (HEVC) typically needs about half the bitrate of H.264, so the video portion of the file is roughly half the size. The audio track doesn't shrink with the video codec, so the total file size reduction is slightly less than a clean 50%.

Is AV1 always the better choice?+

AV1 produces the smallest files at a given quality — often 30-50% smaller than H.265 — but it encodes much slower than H.264 or H.265 and has less universal hardware playback support. For maximum compatibility, H.264 is still the safest export choice; H.265 is a solid middle ground.

Does frame rate change the bitrate I need?+

Yes. Higher frame rates (48-60fps) generally need 30-50% more bitrate than standard 24-30fps to maintain the same visual quality, since there's more motion data to encode every second.

Does the audio track add much to the file size?+

Usually only a small amount. A typical 128-384 kbps audio track adds roughly 1-3 MB per minute — far less than the video track at typical bitrates — but it's still counted in every size calculation here, and it's why halving the video bitrate doesn't exactly halve the total file.

What's the difference between SDR and HDR bitrate recommendations?+

HDR video carries more color and brightness information than SDR, so platforms like YouTube recommend roughly 40-50% more bitrate for HDR than for SDR at the same resolution and frame rate, to avoid visible banding and compression artifacts.

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