Bitrate Calculator – Complete Guide To File Size, Bitrate And Recording Time
The Bitrate Calculator on MyTimeCalculator is designed for creators, editors, streamers and anyone who works with audio or video files. It helps you answer three common planning questions: what bitrate was used for an existing file, how large a new file will be at a chosen bitrate and duration, and how long you can record at a specific bitrate before filling a card or drive.
Behind the scenes, all of these questions rely on the same relationship between bitrate, file size and time. Once you are comfortable with this relationship, you can quickly sanity-check encoding choices and avoid surprises like oversized exports or recordings that stop earlier than expected.
1. The Core Relationship: Bits, Bytes And Seconds
Bitrate describes how many bits are used per second of media. File size describes how many bytes are stored in total. Time describes how long the content runs. Ignoring container overhead, these three quantities are linked by:
The factor of 8 appears because there are 8 bits in a byte. If you know any two of bitrate, size and duration, you can rearrange this relationship to solve for the third. The Bitrate Calculator automates this for you, with unit conversions handled in the background.
2. Computing Bitrate From File Size
If you have an existing file and want to know the average bitrate used to encode it, choose the Bitrate From File Size tab. Enter the file size in KB, MB or GB and the full runtime. The tool converts the storage units to bytes, multiplies by 8 to obtain bits and divides by the duration in seconds.
The calculator reports the result in bps, kbps and Mbps. For audio, common bitrates include 128 kbps, 192 kbps and 320 kbps for MP3, or higher for lossless formats. For video, bitrates can range from a few Mbps for low-resolution web video to tens of Mbps or more for HD and 4K content.
3. Estimating File Size From Bitrate
When planning exports, uploads or deliveries, you often start with a target bitrate and runtime and need to estimate the resulting file size. In the File Size From Bitrate tab, you enter the bitrate in bps, kbps or Mbps and the length of the clip. The calculator multiplies bitrate by duration to get bits and then converts to bytes, MB and GB.
This is particularly useful when you have upload limits or storage constraints. For example, if a platform allows 2 GB per upload, you can experiment with different bitrates to see which settings will keep your file under that cap without sacrificing too much quality.
4. Finding Recording Time From Bitrate And Storage
Camera operators and field recordists often think the other way around: they know the capacity of their memory card or SSD and the bitrate of their recording profile, and they want to know how many minutes or hours they can record. The Recording Time From File Size tab covers exactly this scenario.
You select the card or drive capacity, specify the bitrate and the calculator computes the maximum duration. The result is shown as hours:minutes:seconds as well as total minutes and total hours so you can quickly see whether a given card is enough for a shoot, event or interview block.
5. Bitrate Units: bps, kbps, Mbps, MB And GB
Bitrate is usually measured in bits per second. To keep numbers manageable, prefixes are used:
- kbps = kilobits per second = 1,000 bits per second.
- Mbps = megabits per second = 1,000,000 bits per second.
Storage is usually measured in bytes, which are groups of 8 bits:
- 1 KB ≈ 1024 bytes.
- 1 MB = 1024 KB.
- 1 GB = 1024 MB.
The Bitrate Calculator uses decimal prefixes for kbps and Mbps (based on 1000) and binary steps for storage units (based on 1024), which mirrors the way most software and operating systems present these quantities.
6. Practical Examples
Suppose you want to upload a 15-minute 1080p video and you are considering a bitrate of 8 Mbps. With the calculator, you choose the file-size-from-bitrate tab, enter 8 Mbps and 15 minutes, and learn that the result is a bit over 900 MB. If your upload limit is 1 GB, this will fit comfortably.
Or imagine you have a 128 GB card and plan to shoot at 50 Mbps. Using the recording-time tab, you enter 128 GB and 50 Mbps and obtain a maximum recording time of several hours. You can then decide whether a second card is necessary or whether one card is enough.
7. Tips For Using The Bitrate Calculator Effectively
- Decide which pair of values you know: bitrate and time, size and time, or size and bitrate.
- Select the matching tab and unit choices (kbps vs Mbps, MB vs GB) that match your workflow.
- Enter the values carefully, paying attention to hours, minutes and seconds for longer material.
- Review the outputs in multiple units to get a feel for the scale (for example both MB and GB).
- Leave a little safety margin for container overhead, thumbnails and file system rounding.
8. Limitations And Real-World Considerations
The formulas used in this Bitrate Calculator assume a constant bitrate and ignore container-level overhead. In practice, some formats use variable bitrate (VBR), where the actual bitrate fluctuates around the target value, and containers add a small amount of metadata and index information. As a result, real file sizes can differ slightly from the idealized calculations, but for planning purposes the estimates are very close.
Bitrate Calculator FAQs
Frequently Asked Questions
Quick answers to common questions about bitrate, file size and recording time when working with audio and video.
Bitrate is the amount of data used per second of audio or video. It is usually measured in bits per second (bps), kilobits per second (kbps) or megabits per second (Mbps). Higher bitrates typically allow higher quality but also produce larger files, while lower bitrates save space at the cost of potential compression artifacts or reduced fidelity.
Network and encoding bitrates follow decimal prefixes, so 1 kbps is defined as 1,000 bits per second and 1 Mbps as 1,000,000 bits per second. Storage devices and file sizes are usually measured with binary prefixes, where 1 MB is treated as 1024 KB and 1 GB as 1024 MB. The calculator reflects this mixed convention so that its numbers match what software and operating systems show in practice.
Real media files include container overhead, metadata, thumbnails and sometimes variable bitrate behavior. These factors add or subtract a small amount of data compared with a pure bitrate × time calculation. The Bitrate Calculator gives a close theoretical value that is usually within a few percent of the final size for constant-bitrate encodes and well-behaved variable-bitrate settings.
Yes. If you know the bitrate of your stream, you can use the file-size-from-bitrate tab to estimate how much data will be transferred over a given time period. This is helpful for planning data caps and bandwidth usage. Keep in mind that live streaming platforms may add their own overhead and that adaptive bitrate streaming can change the effective bitrate over time.
The calculator works with a single combined bitrate. If your file has both audio and video streams, you can either add their bitrates together and use the total, or compute sizes separately and then add the resulting file sizes. For quick planning the combined bitrate approach is usually sufficient.