Video File Size Calculator
Estimate a video file size from bitrate and duration, or work backward from a size limit. Picks a bitrate for you from resolution, frame rate, and platform presets.
- Free, no account
- No watermark
- No usage limit
About the Video File Size Calculator
Most video file size calculators have the same blind spot. They ask you for a bitrate in kbps, and if you knew that number off the top of your head you probably would not be looking one up. This tool works backward from what you actually know. Tell it you are exporting a YouTube 1080p video, or set your resolution, frame rate, and codec, and it suggests a bitrate, drops it into the calculator, and shows you the file size. You never have to guess a kbps figure you have no reason to know.
It works two ways. In estimate mode you get the file size from a bitrate and a runtime, handy before a slow export or when you are budgeting storage. Flip to the other mode and it runs backward from a size limit, so a 25 MB email cap and your video length turn into the exact bitrate that fits. Everything updates the moment you stop typing, so there is no render and no test export that runs for twenty minutes before you find out the file is too big.
It all runs in your browser. Nothing you enter is uploaded, there is no sign-up, and once the page has loaded it keeps working with no connection at all. Empty or nonsense entries get a short prompt instead of the confusing NaN a lot of calculators just throw back at you, and impossible cases like a zero-length clip are caught and explained rather than crashing the result. Sizes are in decimal units (1 MB is 1,000,000 bytes) to match what upload dialogs and cloud drives mean by MB and GB.
How to use
- Pick a mode. Choose "Estimate file size" if you know roughly what quality you want and need the size. Choose "Find required bitrate" if you have a hard size limit and need to know what fits it.
- Enter the duration. Type the hours, minutes, and seconds of your final edited clip, not the raw source before trimming. Any combination works, so 90 minutes can go in as 1 hour 30 minutes or as 90 flat.
- Get a bitrate without knowing one. In estimate mode, tap a preset like YouTube 1080p or YouTube 4K, or set the resolution, frame rate, and codec yourself. The suggested bitrate appears, and one tap fills it into the calculator. You can always type your own number over it.
- Or aim at a size. In bitrate mode, tap a limit like Email (25 MB) or type your own target, and read back the total bitrate you need in kbps and Mbps.
- Read the result and share it. The highlighted box shows the answer live. Use Share to copy a link that reopens the exact setup, or Embed to drop the live calculator onto your own site.
Picking a bitrate when you have no idea what to use
Three settings decide how many bits each second of video needs, and the presets set all three for you. When you want to understand what you are choosing, here is how each one pulls.
Resolution is the big one. A 4K frame holds four times the pixels of 1080p, so it needs far more data to look equally sharp. If a preset hands you a 4K bitrate that will not fit your limit, the honest move is usually to drop to 1080p rather than ship a smeary 4K file. On a phone, clean 1080p usually looks better than blurry 4K.
Frame rate pulls next. Sixty frames a second is twice the images of thirty, and it wants roughly 1.5 times the bitrate to stay clean. Screen recordings and talking-head video barely move, so 30 fps looks the same as 60 and costs a lot less. Keep the high frame rates for gaming and sport.
Codec is the setting that changes file size the most for the same quality. H.264 plays on nearly everything but needs the most bits. H.265 gets the same look at close to half the size, and AV1 goes a little further again at the cost of slow encoding and patchier device support. Switch the codec dropdown and watch the suggested number fall. If your file is bigger than it needs to be, changing codec often beats throwing more bitrate at it.
The suggested figures track the upload bitrates the big platforms publish for standard video, so they are safe starting points, not aggressive ones. Grainy footage, confetti, water, fast pans, and tiny screen text all compress badly and can want more. A static slideshow wants far less. Treat the number as a solid first guess and adjust once you have seen a test clip.
Hitting a size limit
A lot of the time the size is not yours to choose. A mail server, a chat app, or a school portal picked it for you. Switch to "Find required bitrate", tap the matching preset or type the cap, enter your runtime, and the tool hands back the bitrate that fits, with a little set aside for audio.
The platform presets in estimate mode and the limit presets here are separate on purpose. Instagram and TikTok re-encode everything you send and cap their own bitrate low, so there is little point sweating a precise number for them. Give them a clean 1080p file and let their pipeline shrink it. Email attachments, offline copies, and portals with a firm ceiling are where the math actually matters, so those are the ones to aim at carefully. For anything above a few gigabytes, a shared link through a drive service is often easier than compressing hard and still moving a large file.
Upload limits also change over time. A chat app that capped uploads at one size last year may sit somewhere else now, so treat the preset as a convenient default and confirm the current number if you are cutting it close.
Frequently asked questions
Why does the suggested bitrate change when I switch codec?
Because codecs differ in how efficiently they pack a given quality. H.265 reaches roughly the same look as H.264 at close to half the data, and AV1 a bit less again. The suggestion multiplies the H.264 baseline by the codec's efficiency, so choosing H.265 drops the number even though the quality target has not moved. The one thing to watch is playback, because older devices and some browsers cannot decode AV1 or H.265, so pick the newest codec your audience can actually play.
Does 60 fps really need more bitrate than 30?
Yes, roughly one and a half times as much for similar quality, because you are encoding twice the frames each second. If your content is mostly still, a slideshow, a webinar, a screen share, drop to 30 fps and you free up that bitrate for nothing lost. Motion is the only thing that justifies 60, so keep it for gameplay, sport, and fast action.
What audio bitrate should I put in?
For speech and most web video, 128 kbps AAC is clean and plenty. Music-heavy content can justify 192 to 256 kbps, and 320 is about the ceiling for lossy audio. It sounds trivial, but on a long clip squeezed into a tight cap the audio share adds up. Dropping a two-hour file from 320 to 128 kbps saves about 173 MB that could go to sharper video instead.
My real export came out a different size than the estimate. Why?
Encoders rarely hold an exact constant bitrate, especially single-pass variable bitrate, and the container adds a small amount of overhead for headers and metadata that raw bitrate math skips. Scene complexity nudges variable encodes up or down too. The estimate usually lands within a few percent. If you need it dead-on, use two-pass encoding, which studies the whole video first and then hits the target closely.
Should I lower the resolution or the bitrate to shrink a file?
Cut the bitrate first if the footage looks clean, since modern codecs handle a lower rate gracefully and a 1080p clip at a modest bitrate often looks fine. Lower the resolution instead when the content is mostly still, like slides or a talking head, where 720p is invisible next to 1080p on a normal screen. Change one at a time and look at the result rather than stacking both cuts blind.
Why are your MB and GB bigger than what my computer reports?
This tool uses decimal units, where 1 MB is 1,000,000 bytes, the convention upload limits and hosting sites use. Windows and some file managers use binary units (1 MiB is 1,048,576 bytes) while still labeling them MB, so their figure looks a touch smaller for the identical file. It is the same file, the two tools just count a megabyte differently.
Can I save or share a calculation?
Yes. The Share button copies a link that carries your mode, duration, and settings, so opening it reopens the exact calculation, which also makes it a handy bookmark. The Embed button gives you a snippet that puts the live calculator on your own page with a small credit back to us. Both keep everything on your side, nothing gets uploaded.