Video Bitrate Calculator

A video bitrate calculator answers three questions that come up constantly in streaming, transcoding, storage planning, and bandwidth budgeting. Given a video bitrate, an audio bitrate, and a duration, how big will the file be? Given a target file size and a duration, what combined bitrate do you need? Given a file size and a connection speed, how long will the upload or download take? All three reduce to one core relation, bytes equal total bitrate times duration divided by 8, and the only complexity is unit conversion, where two distinct traps (bits-vs-bytes and MB-vs-MiB) account for most of the confusion. This calculator does all three modes on one page, shows every result in both decimal and binary multiples, and includes a reference table of typical streaming bitrate ranges labelled as guidance rather than platform specifications.

How to Use the Video Bitrate Calculator

1. Mode 1, file size from bitrate and duration. Type a video bitrate, an audio bitrate, and a duration in seconds. The panel reports the resulting combined stream rate in Mbps, the total bits, the total bytes, and the file size in MB (decimal), MiB (binary), and GB (decimal). This is the forward direction: you know the encoding parameters and want the storage cost.
2. Mode 2, required bitrate from a target file size and duration. Type a target file size (in MB, MiB, GB, or GiB, pick the unit that matches how you think about storage), an audio bitrate, and a duration in seconds. The panel reports the total combined bitrate and the video bitrate remaining after subtracting the audio budget. This is the inverse: you know the storage budget and want the encoder settings.
3. Mode 3, upload / download time. Type a file size and a connection speed in kbps. The panel reports the transfer time in seconds, in minutes, and in human-readable form.
4. Reference table. Click any resolution tier, 480p, 720p, 1080p, or 4K UHD, to see typical streaming bitrate ranges. Use as planning guidance, not targets for any specific platform.
5. Treat every result as a planning estimate. Real-world throughput is typically 70 to 90 % of nominal link speed because of TCP/IP overhead, encryption, retransmits, congestion, and service-side bottlenecks. Real-world file sizes include container overhead and encoder metadata.

The Formulas

Core relation. File size in bytes equals total bitrate in bits per second times duration in seconds, divided by 8 (because 1 byte = 8 bits):

size_bytes = (video_kbps + audio_kbps) * 1000 * seconds / 8

The factor of 1000 converts kbps (kilobits per second, decimal SI) into bit/s. If your bitrate is in Mbps, multiply by 1 000 000 instead of 1 000. The factor of 8 at the end is the single most-omitted term in textbook bitrate / size calculations; missing it gives an answer that is off by almost an order of magnitude.

Mode 1, forward. The formula above is mode 1 in full. The byte count is then divided by the appropriate denominator to report in MB (10⁶), MiB (2²⁰), or GB (10⁹). The relationship between MB and MiB is 1 MiB ≈ 1.048576 MB, a 4.86 % gap that is invisible per second but adds up across hours of video.

Mode 2, inverse. Mode 2 is the algebraic inverse of mode 1. Given a target size and a duration, the total kbps is:

total_kbps = (size_bytes * 8) / (1000 * seconds)

Subtract the audio bitrate to get the video bitrate budget:

video_kbps = total_kbps - audio_kbps

If the audio bitrate would consume the entire budget (or more), the video budget floors at 0, you cannot have a negative video bitrate. In that case the answer reveals that the target size is too small for the duration at the chosen audio rate.

Mode 3, transfer time. The transfer time is the same forward relation solved for time rather than size:

seconds = size_bytes * 8 / (speed_kbps * 1000)

The result is the theoretical minimum transfer time at the nominal link rate. For a 1 GB file over a 100 Mbps link: 1 × 10⁹ × 8 / (100 000 × 1000) = 80 seconds. A real upload typically takes 15 to 40 % longer because of protocol overhead and competing traffic.

Unit reference (NIST SP 811; BIPM SI Brochure 9th ed.; IEC 80000-13 §A.4):

• 1 byte = 8 bits (exact)
• 1 kbps = 1 000 bit/s (decimal SI)
• 1 Mbps = 1 000 000 bit/s
• 1 Gbps = 1 000 000 000 bit/s
• 1 MB = 10⁶ bytes (decimal)
• 1 MiB = 2²⁰ = 1 048 576 bytes (binary, IEC)
• 1 GB = 10⁹ bytes (decimal)
• 1 GiB = 2³⁰ = 1 073 741 824 bytes (binary, IEC)

Worked Examples

Example 1, file size for a 10-minute 1080p stream. Suppose a 1080p encode targets a combined stream of about 5 Mbps (typical for a modern H.264 / HEVC streaming encode at 1080p). Video bitrate 5000 kbps, audio bitrate 128 kbps, duration 600 seconds (10 min).

size_bytes = (5000 + 128) * 1000 * 600 / 8 = 5128 * 1000 * 600 / 8 = 384 600 000 bytes

That is 384.6 MB, or about 366.7 MiB. Storing 100 such 10-minute clips needs about 38.5 GB.

Example 2, 1 GB file over a 100 Mbps link. Transfer time for 1 GB (1 000 000 000 bytes) at 100 000 kbps:

seconds = 1 000 000 000 * 8 / (100 000 * 1000) = 80 seconds

The same 1 GiB (1 073 741 824 bytes) takes about 85.9 seconds, about 7.4 % longer, exactly the gap between GB and GiB.

Example 3, 8 Mbps for one hour. At 8 000 kbps total for 3600 seconds:

size_bytes = 8000 * 1000 * 3600 / 8 = 3 600 000 000 bytes = 3.6 GB

In MiB: 3 600 000 000 / 1 048 576 ≈ 3 433 MiB ≈ 3.35 GiB. About a third of a single-layer DVD's capacity.

Example 4, inverse: 700 MB target over 1800 seconds. A 30-minute show encoded to fit on a 700 MB disc. Target 700 MB, audio 128 kbps, duration 1800 seconds:

total_kbps = (700 * 1 000 000 * 8) / (1000 * 1800) ≈ 3111.1 kbps

Video budget = 3111.1 − 128 ≈ 2983.1 kbps. That is around 3 Mbps, consistent with a 480p or low-720p encode rather than 1080p, which would need at least 2 to 3× that budget for similar perceptual quality.

Example 5, the MiB / MB conversion. A 100 MiB file is 100 × 1 048 576 = 104 857 600 bytes. In MB that is 104.8576 MB. The 4.8576 MB gap is the same as saying "1 MiB ≈ 1.048576 MB", the unit the IEC introduced in 1998 to resolve the ambiguity that had plagued storage labelling since the 1980s. The calculator's mode 2 and mode 3 selectors let you choose MB, MiB, GB, or GiB explicitly so the conversion is never ambiguous.

Example 6, streaming reference comparison. A 1080p stream at 5 Mbps produces 5 000 × 1000 / 8 ≈ 625 000 bytes per second, or 37.5 MB per minute. A 4K UHD stream at 20 Mbps produces 150 MB per minute. An hour of 4K UHD is about 9 GB, consistent with the "60 to 100 GB per 4K movie" rule of thumb at consumer-streaming bitrates.

Where Bitrate Calculations Show Up

Streaming and VOD encoding. Picking a target bitrate for an encoder is the inverse of asking "how big will the file be at this rate", both questions are mode 1 / mode 2 calculations. The chosen bitrate depends on codec efficiency, content type, and target quality.

Storage planning. Estimating how many hours of footage fit on a drive or in a CDN bucket is mode 1 applied to each stream. A 1 TB drive holds about 23 hours of 1080p at 5 Mbps, or about 5 hours of 4K UHD at 20 Mbps, roughly 4 to 5× the storage for the 4× pixel-count upgrade.

Bandwidth budgeting. Estimating upload time to a cloud bucket, or how long a viewer waits to download a file at a given connection speed, is mode 3. For a 10 GB file over 100 Mbps: about 800 seconds (13 minutes). Real-world throughput is typically 70 to 90 % of nominal.

Network capacity planning. Computing whether a link can sustain N simultaneous streams at a given bitrate is mode 1 applied N times. A 1 Gbps link sustains about 200 simultaneous 5 Mbps streams at full utilisation; realistic targets are 60 to 80 % of link capacity.

Live event sizing. Multi-camera live events use mode 1 summed across cameras and stream variants. A 4-camera 4-hour event with 1080p main and 720p preview streams produces roughly 4 × (5 + 1.5) × 14 400 / 8 ≈ 47 GB, ignoring container overhead.

CDN and egress costing. Cloud egress is priced per GB transferred. Mode 1 × N views × bitrate tells you how many TB of egress a viral video will generate, which is what your CDN bill scales with.

Common Mistakes

Confusing Mbps with MB/s. A 100 Mbps connection transfers 100 megabits per second = 12.5 megabytes per second. A "100 MB file" over a "100 Mbps link" takes 8 seconds, not 1. This is the most common reason people think their fast internet is slow for large files.

Confusing MB with MiB. A "1 MB" file is 1 000 000 bytes on most consumer software, but 1 048 576 bytes on older Windows. The IEC binary prefixes (KiB, MiB, GiB) exist to resolve this. 1 MiB is about 4.86 % bigger than 1 MB, small per file, large over hours of video.

Ignoring the factor of 8. Multiplying bitrate by duration gives bits, not bytes. Dividing by 8 is the most-skipped step in textbook calculations. A 5 Mbps stream over an hour is 2.25 GB, not 18 GB.

Ignoring audio bitrate. Typical streaming audio (96 to 192 kbps) is small compared to 5 Mbps video but becomes significant at lower video rates, at 200 kbps video with 128 kbps audio, audio is 39 % of the budget.

Ignoring container overhead. MP4/MKV/MOV add 1 to 3 % metadata, index, and timing beyond elementary streams. Plan for 1 to 5 % overhead on top of calculated sizes.

Assuming VBR = constant bitrate. VBR allocates more bits to complex scenes. Average bitrate drives size; peak bitrate (often 2 to 5× the average) must fit the streaming bandwidth but does not change file size.

Using peak bitrate for file-size calculations. File size scales with average bitrate, not peak. Using peak gives a 2 to 5× overestimate. The reference table values are typical averages, not peak ceilings.

Reading "MB" on a Windows "Properties" dialog. Windows historically displayed binary multiples (MiB) labelled as "MB", the source of much confusion when comparing to macOS / Linux / drive-label sizes. The mode 2 and mode 3 unit selectors cover all four labels.

Codec and Content Notes

The reference table gives typical ranges for general consumer streaming, not targets for any specific platform. Real recommendations vary by codec (H.264 < HEVC < AV1 for the same perceptual quality, each generation delivering comparable quality at 30 to 50 % lower bitrate), content type (talking head < animation < sports < film grain, high-frequency texture resists compression), frame rate (50/60 fps needs proportionally more bitrate than 24/30 fps), and quality target (visual transparency requires roughly 2 to 3× the bitrate of acceptable streaming quality). For VBR encoding, file size scales with the average bitrate, not the peak; the peak can be 2 to 5× the average in difficult scenes.

Frequently Asked Questions

What is the difference between Mbps and MB/s?

Mbps (megabits per second) measures connection or bitrate speed; MB/s (megabytes per second) measures data throughput. The relationship is fixed: 1 byte = 8 bits, so 1 MB/s = 8 Mbps. A 100 Mbps link transfers at up to 12.5 MB/s in practice (and often less, due to overhead). Confusion between the two is the most common reason people underestimate transfer times.

What is the difference between MB and MiB?

MB is the decimal megabyte = 1 000 000 bytes (used by most consumer software, hard-drive labels, and network speeds). MiB is the binary mebibyte = 2²⁰ = 1 048 576 bytes (the IEC binary prefix, often displayed as "MB" by Windows). 1 MiB ≈ 1.048576 MB, a 4.86 % gap that compounds across hours of video. Modern macOS, Linux, and recent Windows versions label MiB explicitly.

How do I calculate the file size of a video from its bitrate?

Multiply the combined bitrate (video + audio, in bits per second) by the duration in seconds, then divide by 8 to get bytes. For a 5 Mbps video stream with 128 kbps audio over 600 seconds: (5000 + 128) × 1000 × 600 / 8 = 384 600 000 bytes, or 384.6 MB (decimal). This is mode 1 of the calculator.

How do I calculate the bitrate needed for a target file size?

Invert the same relation: total kbps = (target_bytes × 8) / (1000 × seconds). For a 700 MB target over 1800 seconds: (700 000 000 × 8) / (1000 × 1800) ≈ 3111 kbps total. Subtract the audio bitrate to get the video budget (about 2983 kbps if audio is 128 kbps). This is mode 2 of the calculator.

How long does it take to upload or download a video file?

Transfer time in seconds = (file_bytes × 8) / (connection_kbps × 1000). For 1 GB over 100 Mbps: 80 seconds. Real-world time is typically 15 to 40 % longer because of protocol overhead (TCP/IP, encryption, retransmits), congestion, and the service-side bottleneck. This is mode 3 of the calculator.

What bitrate should I use for 1080p streaming?

There is no single answer, it depends on codec, content, and target quality. As a typical consumer-streaming range, 1080p video sits between roughly 3 Mbps and 6 Mbps combined bitrate. H.264 high-profile tends toward the higher end (4 to 6 Mbps); HEVC and AV1 toward the lower end (2 to 4 Mbps) for comparable perceptual quality.

What about 4K UHD streaming?

4K UHD at consumer-streaming quality typically uses 12 to 25 Mbps combined bitrate, roughly 3 to 5× the bitrate of 1080p for comparable perceptual quality. The higher range (20 to 45 Mbps) is for film-grain or motion-heavy content; the lower end (12 to 15 Mbps) is for codec-efficient HEVC/AV1 encodes of simpler content. An hour of 4K UHD at 20 Mbps is roughly 9 GB.

Does the calculator account for variable bitrate (VBR)?

The calculator assumes constant bitrate (CBR). For VBR, file size scales with the average bitrate, not the peak. The reference table ranges are typical averages for consumer streaming, not peak ceilings. For a precise VBR estimate, use your encoder's output statistics after a representative encode.

Why does my encoded file not match the calculated size?

Container overhead (MP4/MKV/MOV metadata, index tables, timing) typically adds 1 to 3 % beyond the elementary stream sizes. Audio tracks, subtitle tracks, and chapter markers add more. Encoder lookahead buffers and rate-control smoothing can shift bit allocation by a few percent in either direction. Plan for 1 to 5 % overhead beyond the calculated size.

Can this calculator be used for professional or commercial encoding work?

Yes, the calculator produces mathematically correct results from the standard SI bit / byte conversions and is suitable for professional encoding, storage planning, and bandwidth budgeting. For high-stakes applications (broadcast specifications, regulatory compliance), verify the output against the specific codec and container you are targeting, different containers and codec profiles have different overhead characteristics.

For the Video Bitrate Calculator, File Size, Required Bitrate & Transfer Time, How often are the underlying formulas updated?

The formulas are based on NIST SP 811, the BIPM SI Brochure, and IEC 80000-13, all stable, well-established standards. The 1 byte = 8 bits relation is exact; the decimal-vs-binary unit distinctions are settled by the IEC binary prefix standard. The typical streaming bitrate ranges are general consumer guidance that shifts gradually with codec adoption (HEVC, AV1) but the underlying math is unchanged.

References

• NIST Special Publication 811, Guide for the Use of the International System of Units (SI). The authoritative US reference for SI usage, including the decimal multiples for bit rates (kbps, Mbps, Gbps) and the exact factors for byte multiples.
• BIPM SI Brochure (9th edition), The International System of Units (SI). The canonical SI reference published by the Bureau International des Poids et Mesures, defining the decimal prefixes used throughout this calculator.
• IEC 80000-13, Quantities and units, Part 13: Information science and technology. Defines the IEC binary prefixes (KiB, MiB, GiB) and the 1 byte = 8 bits relation that the calculator relies on.
• IEC 61966-2-1, Multimedia systems and equipment, Colour measurement and management, Part 2-1: Colour management, Default RGB colour space, sRGB. Cited here as a representative IEC multimedia standard; the bitrate / size conversions themselves are codec-independent.
• ISO/IEC 13818, MPEG-2. The generic MPEG-2 standard, referenced here for general bitrate terminology used across MPEG-family codecs.
• ISO/IEC 14496, MPEG-4. The MPEG-4 standard family, including the H.264/AVC codec and the MP4 container format. The bitrate / size relations are codec-independent and identical to those used in MPEG-2.
• General consumer-streaming guidance, The typical streaming bitrate ranges in the reference table (0.5 to 1.5 Mbps for 480p, 1.5 to 3 Mbps for 720p, 3 to 6 Mbps for 1080p, 12 to 25 Mbps for 4K UHD) are general planning guidance compiled from public consumer-streaming documentation. They are NOT specifications for any particular platform, codec, or device. Real platform recommendations vary by codec (H.264 vs HEVC vs AV1), content type, and target quality. For a specific deployment, consult the platform's current published recommendations.