How Big Is a YouTube Video File? What Decides the Size

The one formula behind every file size

There is no fixed size for "a 1080p YouTube video". Every video file is the same simple product:

file size = bitrate × duration

Bitrate is how much data the encoder spends on each second of video, measured in megabits per second (Mbps). Divide by 8 to get megabytes. A handy shortcut: multiply the bitrate in Mbps by 7.5 to get megabytes per minute.

Some round numbers to build a feel for it:

• 1 Mbps is about 7.5 MB per minute, or roughly 450 MB per hour
• 2 Mbps is about 15 MB per minute, or roughly 900 MB per hour
• 4 Mbps is about 30 MB per minute, or roughly 1.8 GB per hour
• 8 Mbps is about 60 MB per minute, or roughly 3.6 GB per hour
• 16 Mbps is about 120 MB per minute, or roughly 7.2 GB per hour

These are arithmetic examples, not claims about what YouTube uses. The real bitrate depends on the video, which is the useful part to understand.

What changes the bitrate

Resolution. More pixels need more data, so 1080p is bigger than 720p, and 4K is much bigger again. The jump is large, because 4K has four times the pixels of 1080p.

Codec. Two files of the same resolution and quality can differ a lot in size depending on whether they use H.264, VP9 or AV1. Newer codecs generally need less data for similar quality, which is why you will often see several rows at the same resolution with different sizes. We cover the differences in YouTube video formats explained.

Frame rate. A 60 fps stream has twice as many frames to describe as a 30 fps one, so it is usually noticeably larger.

What is on screen. This is the factor people overlook. Slow, mostly static footage compresses far better than fast action, particle effects or lots of fine detail. Two videos with the same length, resolution and codec can differ several times in size.

Why a merged file is bigger than the video stream alone

Above 480p, YouTube usually stores video and audio as separate streams. A "video only" row shows only the picture, and the finished file adds an audio stream as well. The final size is roughly the two added together, plus a small amount of container overhead.

Real numbers from our own test files

We checked this on the same 3 minute 33 second music video:

• The video merged with its audio at a 720p cap came to about 21 MB. That is roughly 0.8 Mbps overall, which is low for 720p and shows how much a static-looking video can be compressed.
• The audio-only Opus stream for the same video was about 3.4 MB, roughly 130 kbps. We cover audio bitrates in YouTube audio quality explained.

One video is a small sample, and a fast-moving game or sports clip of the same length would be several times larger. It illustrates the formula, and shouldn't be used to predict your own file.

How to find out before you download

You don't have to guess. The format list on our YouTube video downloader shows a size for each row before you download anything. Some sizes are marked approximate, because YouTube does not always publish exact figures for a stream. Compare rows at the same resolution to see what each codec costs you, and pick the smallest one your device can play.

A few practical rules of thumb:

• Downloading to keep on a phone with limited space: pick 720p, or the smallest codec your phone supports.
• Archiving something you may edit later: pick the highest resolution and accept the size.
• Saving only the sound: audio-only streams are a fraction of the size of video.