Free video file size calculator: enter bitrate and duration to estimate MB and GB before you export. Formula, bitrate tables, and codec tips included.
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Enter your values and press Calculate.
Enter the video bitrate in Mbps and the duration in minutes. The calculator converts minutes to seconds, multiplies bitrate × duration, and divides by 8 to turn bits into bytes: size (MB) = bitrate (Mbps) × duration (seconds) / 8. It also converts to GB (MB / 1024) and shows the size per minute. Use the reference bitrate table on the page if you do not know your bitrate. The result is an estimate: variable bitrate encoding, audio tracks, and container overhead move the final export a little either way.
A video file is a stream of bits played back over time, so its size comes from two numbers: the bitrate (how many bits per second) and the duration (how many seconds). Multiply them and you get total bits; divide by 8 to convert bits to bytes. The formula is: size (MB) = bitrate (Mbps) × duration (seconds) / 8. Example: 8 Mbps held for 10 minutes (600 seconds) gives 8 × 600 / 8 = 600 MB. The calculator above does this in one step and also converts the answer to GB.
The most common mistake is mixing up Mbps (megabits per second) with MBps (megabytes per second). Bitrate is measured in bits: 8 Mbps means 8 million bits per second, which is only 1 megabyte per second. That factor of 8 is why a 10 Mbps stream fills a 75 MB file in one minute (10 × 60 / 8 = 75), not a 600 MB one. Always check the capitalisation: a small b means bits, a big B means bytes.
Bitrate presets are the typical values for good-quality encodes; high-motion content needs a higher bitrate for the same quality. For H.264 at 30fps, widely used recommendations are: 720p, 5 Mbps; 1080p, 8 Mbps; 1440p, 16 Mbps; 4K, 35 to 45 Mbps; 8K, 100 to 150 Mbps. YouTube suggests roughly 8 Mbps for 1080p uploads and 35 to 45 Mbps for 4K uploads at standard frame rates. Use these as starting points in the calculator, then adjust for your content.
The codec decides how efficiently pixels are compressed, so the same footage at the same visual quality needs very different bitrates. H.264 (AVC) is the most widely compatible codec and the baseline for every table on this page. H.265 (HEVC) delivers the same quality at roughly half the bitrate, so files run 40 to 50 percent smaller. AV1 is free and open and pushes efficiency further, to about 45 percent of the H.264 bitrate, though device support is still catching up. VP9, used by YouTube, sits close to H.265. Newer codec, same quality, much smaller file.
Constant bitrate (CBR) holds the same bitrate for the whole video, so the formula predicts it almost exactly. Variable bitrate (VBR) spends more data on complex scenes and less on simple ones, producing better quality at the same average file size, or a smaller file at the same quality. Most modern encoders default to VBR, which is why exports often land a little above or below the estimate. Scene complexity, encoder settings, and container overhead explain the rest of the gap.
A video file is not pure video data: the container holds metadata, indexes, subtitles, and usually an audio track. Audio at a typical 128 to 320 kbps adds a few megabytes per 10 minutes, and container overhead is roughly 1 to 5 percent of the file. On a 600 MB estimate that means a few megabytes either way. The calculator focuses on the video stream, which dominates the total, so add a small margin when storage is tight.
Step 1: convert the duration to seconds. 10 minutes × 60 = 600 seconds. Step 2: multiply bitrate by duration. 8 Mbps × 600 s = 4800 megabits. Step 3: divide by 8 to get megabytes. 4800 / 8 = 600 MB. Step 4: convert to GB. 600 / 1024 = 0.59 GB. A handy rule of thumb falls out of this: one minute of 1080p at 8 Mbps is about 60 MB, and one minute of 4K at 45 Mbps is about 340 MB.
Scale the formula to plan shoots and archives. One hour of 1080p at 30fps in H.264 needs about 3.6 GB; the same hour in 4K needs around 15 GB. A two-hour 1080p movie encoded in H.265 runs about 3.6 GB, while 10 minutes of 4K in H.265 is roughly 1.5 GB. A practical rule: keep two to three times your calculated storage free, to cover multiple takes, VBR overshoot, and project files alongside the video. Run these numbers before a recording session to work out how much storage you need, so you pick an SD card or drive with capacity to spare.
Lower the bitrate: the most direct lever, though quality drops if you push it too far. Switch to a modern codec: H.265 or AV1 cuts the file roughly in half at the same visual quality. Match the resolution to the destination: exporting 4K when the video will only ever play at 1080p wastes storage. Trim unnecessary footage: shorter duration shrinks the file proportionally. Use VBR encoding: it spends bits where the eye notices them and saves where it does not.
Drive makers and some tools count 1 GB as 1,000,000,000 bytes (decimal), while operating systems traditionally count 1 GiB as 1,073,741,824 bytes (binary). That 7 percent gap is why a 600 MB file shows as 0.59 GB on a binary-counting system but 0.60 GB on a decimal one. This calculator reports GB the binary way (MB / 1024), matching what Windows and most storage meters display.
Enter the video bitrate in Mbps, for example 8 for a typical 1080p H.264 export. Enter the duration in minutes, for example 10. Press calculate to get the estimated file size in MB and GB, plus the size per minute as a quick reference. Use the bitrate table above if you do not know your bitrate, and pick a lower bitrate or a modern codec if the estimate is bigger than your storage allows.
Multiply the bitrate in Mbps by the duration in seconds, then divide by 8: size (MB) = bitrate × seconds / 8. Example: 10 Mbps for 60 seconds gives 10 × 60 / 8 = 75 MB. The calculator above does the math and converts to GB automatically.
No. Mbps (megabits per second) is 8 times smaller than MBps (megabytes per second). Bitrate is measured in bits, so always divide by 8 when converting to the megabytes your storage meter shows.
YouTube recommends roughly 8 Mbps (8,000 kbps) for 1080p and 35 to 45 Mbps for 4K at standard frame rates. YouTube re-compresses your upload afterward regardless, so there is no benefit in going far above these targets.
Most encoders use variable bitrate (VBR) rather than a perfectly constant rate, and container overhead, audio tracks, and subtitles add a little on top. Scene complexity also matters: fast motion needs more data than static shots. The estimate is usually within a few percent; test-encode a short clip for critical storage planning.
Use H.264 for maximum compatibility: it plays everywhere. Use H.265 when storage is limited and your audience uses modern devices: files run 40 to 50 percent smaller at the same visual quality. AV1 goes further but has the weakest device support of the three.
CBR (constant bitrate) holds the same bitrate throughout, which is good for live streaming where steady bandwidth matters. VBR (variable bitrate) gives complex scenes more data and simple scenes less, producing better quality at the same average file size. VBR is usually the better choice for files you export and keep.
At a typical 8 Mbps it is about 3.6 GB per hour in H.264 (8 / 8 × 3600 = 3600 MB). At a lean 5 Mbps streaming bitrate it is about 2.2 GB. Switching to H.265 roughly halves both figures.
On Windows, right-click the file, open Properties, and look under the Details tab. On Mac, use Get Info. In VLC, open Media Information and check the Statistics tab during playback. Video editors and tools like HandBrake also show the bitrate when you open a file.
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