"How many GB is an hour of video?" has no single answer, and the range is enormous. An hour-long video call recording can be under half a gigabyte. An hour of iPhone video at 1080p is about 3.6 GB. Switch the same iPhone to 4K at 60 frames per second and it's about 24 GB. Record in Apple's ProRes format and it's roughly 360 GB - a hundred times more than the 1080p version, for the same hour.
All of that variation comes down to one number: the bitrate, or how much data the video uses per second. Once you know a video's bitrate, its size is simple arithmetic.
#The one formula you need
Bitrate is measured in megabits per second (Mbps). To turn it into a file size:
- MB per minute = Mbps × 7.5
- GB per hour = Mbps × 0.45
So an 8 Mbps video - typical for 1080p from a phone - uses 60 MB a minute and 3.6 GB an hour. (The 7.5 comes from 60 seconds divided by 8, because there are 8 bits in a byte.) Audio adds very little on top: even generous 256 kbps sound is under 2 MB a minute. If you want the full picture of what bitrate does to quality as well as size, Video bitrate explained covers it in plain English.
How much space an hour of video takes
| Source | Bitrate | Per minute | Per hour |
|---|---|---|---|
| Video call recording (720p) | about 1 Mbps | 5-8 MB | 0.3-0.5 GB |
| HD streaming (Netflix) | up to 6.7 Mbps | up to 50 MB | up to 3 GB |
| iPhone 1080p, 30 fps | about 8 Mbps | about 60 MB | about 3.6 GB |
| 4K streaming (Netflix) | up to 15.6 Mbps | up to 115 MB | up to 7 GB |
| iPhone 4K, 60 fps | about 53 Mbps | about 400 MB | about 24 GB |
| GoPro 4K / 5.3K | 60-120 Mbps | 450-900 MB | 27-54 GB |
| iPhone 4K ProRes | about 800 Mbps | about 6 GB | about 360 GB |
#Why the same length can be ten times the size
- Resolution. 4K has four times the pixels of 1080p, and typically needs several times the bitrate to look as good.
- Frame rate. 60 frames per second is twice as many pictures as 30, so it needs more data - not quite double, because consecutive frames are very similar.
- The codec. HEVC (what iPhones use in their default "High Efficiency" mode) needs about 40% less data than H.264 for the same quality. Switching an iPhone to "Most Compatible" makes every video noticeably bigger.
- Recording versus delivery. Cameras and phones encode in real time, so they use plenty of bitrate to be safe. Streaming services encode each film once, slowly and carefully, so they get good quality from far less data. That's why an hour of Netflix in 4K is smaller than ten minutes of 4K from your phone.
- What's on screen. A screen recording of a slide deck barely changes from frame to frame and compresses well. Confetti, rain, water and fast sport are the hardest things to compress.
#How much video fits on your phone or memory card
Hours of video per storage size
| Storage | 1080p at 30 fps (60 MB/min) | 4K at 60 fps (400 MB/min) |
|---|---|---|
| 64 GB | about 18 hours | about 2.7 hours |
| 128 GB | about 35 hours | about 5.3 hours |
| 256 GB | about 71 hours | about 10.7 hours |
| 512 GB | about 142 hours | about 21 hours |
#Why your computer shows a smaller number
Storage makers and phone settings count a gigabyte as 1,000,000,000 bytes. Windows File Explorer counts it as 1,073,741,824 bytes (1,024 × 1,024 × 1,024), while still calling it "GB". So a 3.6 GB video shows up in Windows as about 3.35 GB, and a "128 GB" memory card as about 119 GB. Nothing is missing - it's two definitions of the same word. Macs have used the storage makers' definition since 2009, so their numbers match the box.
#Making video files smaller
Since size is bitrate times length, there are only a few levers:
- Record smarter. Use High Efficiency (HEVC) on an iPhone, and 1080p instead of 4K for anything that will only ever be watched on a phone. 4K at 60 fps is worth it for footage you'll edit or watch on a big screen; for everyday clips it's a lot of storage for little visible gain.
- Convert old or inefficient formats. Motion JPEG from dashcams, ProRes from editing apps and older formats like DV are many times bigger than H.264 at the same visual quality. Converting them to an H.264 MP4 with Wave typically shrinks them 10-20 times - MJPEG to MP4 and ProRes to MP4 show the numbers. Wave's inspect screen shows the estimated output size and time before you convert, and the file is never uploaded.
- Re-encode at a lower bitrate. For a video that's already H.264 or HEVC, the only way to shrink it further is to re-compress it with less data. Compress MP4 and Reduce MP4 file size walk through the maths and the free tools that do it.
#The short version
- File size depends on bitrate: MB per minute = Mbps × 7.5, GB per hour = Mbps × 0.45.
- An hour of iPhone video is about 3.6 GB at 1080p and about 24 GB at 4K 60 fps. ProRes is about 360 GB.
- A 128 GB phone holds roughly 35 hours of 1080p or 5 hours of 4K at 60 fps, minus what the system uses.
- Windows shows sizes about 7% smaller than the box says, because it counts gigabytes differently.