Video File Size Calculator

TL;DR: To calculate video file size, multiply the video duration (in seconds) by the bitrate (in kbps), then divide the result by 8,192 to convert it to Megabytes (MB) — or simply use the formula: File Size (MB) = (Duration in seconds × Bitrate in kbps) / 8,192.

What Is the Video File Size Calculator?

The Video File Size Calculator is a free online tool that instantly estimates the storage space required for a digital video file. Instead of guessing or manually crunching large numbers, you input two core variables — the duration of the video and its bitrate — and the tool outputs the exact file size in Megabytes (MB).

This calculator is essential for video editors, content creators, IT administrators, and anyone who needs to manage storage quotas, estimate upload times, or ensure a video fits within platform-specific file limits (e.g., 25 MB for email attachments or 2 GB for certain video hosting services). It removes the trial-and-error process of exporting a video, checking its size, and re-exporting it repeatedly.

Because the calculation is based on the technical definition of digital data flow (bitrate), the result is highly accurate for compressed and uncompressed video streams alike, provided you know the correct bitrate value for your file.

How to Use the Calculator

Using the tool is straightforward and requires only two numeric inputs. Follow this step-by-step guide to get your result in under a minute:

1. Enter the Video Duration: Type the total length of your video in seconds into the 'Duration' field. For example, a 3-minute clip is 180 seconds (3 × 60). If your video is longer than an hour, multiply the hours by 3,600 and add the remaining seconds to get a single value.
2. Enter the Bitrate: Input the video bitrate in kilobits per second (kbps) into the 'Bitrate' field. This value is usually specified in your video editing software's export settings or in the metadata of an existing file. For reference, a typical 1080p video on YouTube uses a bitrate of around 8,000 kbps.
3. Click 'Calculate': Press the calculate button. The tool will instantly process the values using the standard conversion formula.
4. Read the Output: The result will be displayed in Megabytes (MB). This represents the estimated size of the video file, excluding any separate audio tracks or metadata containers unless specified.

There are no hidden settings or configuration steps. Simply adjust the two inputs if you want to compare different quality settings (e.g., 5,000 kbps vs. 10,000 kbps) to see how much storage you would save.

Formula and Calculation Method

The underlying mathematics of this calculator are rooted in the fundamental relationship between data rate, time, and storage. The formula works in three logical phases, which we explain below in plain language.

The Formula: File Size (MB) = (Duration in seconds × Bitrate in kbps) ÷ 8 ÷ 1024

This can be combined into a single step: File Size (MB) = (Duration × Bitrate) / 8192.

Calculation Breakdown:

• Step 1 (Multiply): Multiply the total duration (in seconds) by the bitrate (in kbps). This gives you the total number of kilobits contained in the entire video stream. For example, 60 seconds × 5,000 kbps = 300,000 kilobits.
• Step 2 (Convert bits to bytes): Divide the total kilobits by 8. Since there are 8 bits in a single byte, this converts the raw data rate into kilobytes. In our example, 300,000 ÷ 8 = 37,500 kilobytes.
• Step 3 (Convert to Megabytes): Divide the kilobytes by 1,024. This is the binary conversion factor (1 MB = 1,024 KB). In our example, 37,500 ÷ 1,024 = 36.62 MB.

Worked Example: Let us calculate the size of a 60-second video with a bitrate of 5,000 kbps.
1. 60 seconds × 5,000 kbps = 300,000 kilobits.
2. 300,000 ÷ 8 = 37,500 kilobytes.
3. 37,500 ÷ 1,024 = 36.62 MB.
Therefore, the estimated file size is 36.62 MB.

Practical Examples

The calculator is flexible enough to handle various real-world scenarios. Below are three distinct use cases that reflect common editing and sharing situations.

Notice how the duration and bitrate scale linearly. If you double the bitrate, the file size doubles. If you halve the duration, the file size halves. This predictability allows you to estimate the bitrate you need to hit a specific file size limit for a known duration.

Tips for Accurate Results

To ensure that the calculator gives you a result that matches your actual file on disk, you must be aware of the technical nuances of video encoding. Here are the most critical tips to avoid discrepancies.

• Do Not Confuse kbps with KB/s: The calculator relies on input in kilobits per second (kbps). A common error is entering the download speed (e.g., '5 MB/s') or using the file transfer speed symbol 'KB/s' (KiloBytes per second). Since 1 KB/s = 8 kbps, a file encoded at 8,000 kbps is actually transferring at 1,000 KB/s. Always check that your source displays 'kbps' or 'Kbps', not 'KB/s'.
• Account for Separate Audio Tracks: The formula above calculates the file size for the video stream only. Many videos include a separate audio stream (e.g., AAC, MP3). If the audio bitrate is 320 kbps and the duration is 60 seconds, you must add an extra (320 × 60) / 8192 = 2.34 MB to the total. The calculator assumes the bitrate you entered is the total bitrate (video + audio) unless you are solely working with a silent video. Read your encoder settings carefully.
• Use the Actual Bitrate, Not the 'Nominal' Bitrate: Variable bitrate (VBR) encoding means the actual bitrate fluctuates. For accurate size estimation, use the average bitrate reported by your media player or editing software (often found in file properties). Using the maximum bitrate will overestimate the size.
• Be Wary of Container Overhead: The result is the estimated size of the raw data stream. The final file container (e.g., .mp4, .mov) adds a tiny amount of overhead (a few kilobytes to a few megabytes depending on metadata). For videos under 500 MB, this overhead is negligible; for 2-hour movies, it might add 1–2 MB extra.

Frequently Asked Questions

Why is my actual video file size larger than the calculator result?

There are two primary reasons for a discrepancy. First, you likely are including an audio stream in your container. A 10-minute video at 10,000 kbps video bitrate equals 7.32 MB per minute (600 seconds / 8192 × 10,000 = 732 MB). If your audio is 256 kbps, it adds roughly 1.87 MB per minute, pushing the total higher. Second, your encoder might be using a higher bitrate than you specified for complex scenes (VBR overshoot). To match the calculator, ensure your encoder is set to a Constant Bitrate (CBR) and that you add the audio bitrate to the video bitrate before entering it into the calculator.

Can I use this calculator to figure out how long I can record on a memory card?

Yes, absolutely. This is a reverse-engineering use of the same formula. If you have a 32 GB memory card (approximately 32,000 MB), and you know your camera records at a bitrate of 24,000 kbps, you can calculate the maximum duration. Rearranging the formula gives: Duration (seconds) = (File Size in MB × 8,192) / Bitrate. In this case: (32,000 × 8,192) / 24,000 = 10,922 seconds, or roughly 3 hours and 2 minutes. The calculator is designed to output size, but you can adjust the inputs mathematically to solve for duration instead.

What is the difference between a bitrate of 1,000 kbps and a bitrate of 8,000 kbps?

The difference is in visual quality and data consumption. An 8,000 kbps file is exactly 8 times larger than a 1,000 kbps file for the same duration. For example, a 60-second video at 1,000 kbps will be 7.32 MB. The same duration at 8,000 kbps will be 58.59 MB. The lower bitrate is suitable for screen recordings or animated presentations with little motion; the higher bitrate is needed to preserve detail in fast-moving scenes (e.g., sports or action movies). Higher bitrates also download and upload slower, requiring more bandwidth. The calculator helps you find the sweet spot where the file size is manageable but the quality is still acceptable.