Video File Size Calculator
Estimate a video's file size from its bitrate and length.
Megabits per second — check your export settings.
Results update as you type.
How it works
A video file size calculator estimates how large a video file will be from its bitrate and duration. Bitrate, measured in megabits per second, is the amount of data the video uses each second, and it is the single biggest factor in both file size and visual quality. Knowing the resulting size in advance helps you plan storage, gauge upload times, and confirm a file will fit within a platform's limits before you export or transfer it. This estimate is valuable across video work. An editor choosing export settings wants to know whether a project will fit on a drive or under an email attachment limit. A creator uploading to a platform with a size cap needs to confirm the file qualifies. Anyone archiving footage can project how much storage a library will need. Because bitrate drives both quality and size, seeing the trade-off in gigabytes makes it concrete when deciding how aggressively to compress. The calculation works because a constant-bitrate video's size equals its data rate multiplied by its length. Multiplying bitrate in megabits per second by the duration in seconds gives total megabits, dividing by eight converts to megabytes, and dividing by 1,024 gives gigabytes. Variable-bitrate encoding makes real files fluctuate around this figure, and container overhead adds a little, so treat the result as a close estimate. Editors, videographers, and anyone managing video use a file size calculator to plan storage and uploads with confidence.
size (GB) = bitrate (Mbps) × minutes × 60 ÷ 8 ÷ 1,024
A video's size is set by how many bits it uses each second, the bitrate, multiplied by how many seconds it runs. Multiplying the bitrate in megabits per second by the duration in seconds gives total megabits; dividing by eight converts megabits to megabytes, since a byte is eight bits. Dividing megabytes by 1,024 gives gigabytes. The method works because at a constant bitrate, file size is simply the data rate times the running time.
Source:Standard digital media (bitrate × duration)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter video length and bitrate.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
File size updates instantly as you type — no button to press.
Frequently asked questions
What is bitrate and where do I find it?
Bitrate is the amount of data a video uses per second, measured in megabits per second (Mbps). You set it in your editor's or camera's export and recording settings, where it may be called target bitrate or data rate. Streaming services and cameras publish typical values: 1080p often uses 8 to 12 Mbps, while 4K may use 35 to 60 Mbps. Higher bitrate means better quality and a larger file.
Why divide by 8 in the formula?
Bitrate is stated in megabits per second, but file sizes are measured in megabytes, and one byte equals eight bits. Dividing the total megabits by eight converts the figure into megabytes. This bits-versus-bytes distinction trips many people up: a connection rated at 80 megabits per second transfers only about 10 megabytes per second. Keeping the units straight is essential to getting an accurate file size from a bitrate.
Does higher bitrate always mean better quality?
Up to a point. Higher bitrate preserves more detail and reduces compression artefacts, improving quality, but there are diminishing returns once the bitrate exceeds what the content needs. Beyond that, you add file size without any visible benefit. The ideal bitrate depends on resolution, frame rate, and how much motion the footage contains. Fast-moving or highly detailed video needs more bitrate than a static talking-head shot to look equally clean.
Why is my actual file a slightly different size?
Most modern encoders use variable bitrate, which raises the data rate for complex scenes and lowers it for simple ones, so the real average differs from your target. The container format also adds a small amount of overhead for audio, metadata, and structure. This calculator assumes a constant bitrate for a clean estimate, so expect real files to land close to but not exactly on the predicted size.
How do I make a video file smaller?
Lower the bitrate, which directly shrinks the file, though too low introduces visible artefacts. Reduce the resolution or frame rate if the target platform allows. Use a more efficient codec such as H.265 or AV1, which achieve the same quality at a lower bitrate than older H.264. Trimming unnecessary footage also helps. Balance these against acceptable quality, using this calculator to check the size each bitrate choice produces.