HEVC Bitrate Calculator: How to Use It

This calculator estimates the bitrate you need for HEVC (H.265) video encoding based on resolution, frame rate, and your target file size or quality preference. Enter your video’s resolution, frame rate, and desired duration (or file size), and it returns the required bitrate in megabits per second (Mbps) and the resulting file size for a given bitrate. It helps you balance visual quality against storage or bandwidth constraints before you start an encode.

Formula

The core formula for calculating bitrate from file size and duration is:

Bitrate (Mbps) = (File Size in Megabits) / (Duration in seconds)

Since file size is usually given in gigabytes (GB) and duration in minutes, the practical formula used above is:

Bitrate (Mbps) = (File Size in GB × 8192) / (Duration in minutes × 60)

Where:

• File Size (GB) – the total size you want the output video to be (1 GB = 8192 megabits, not 8000, because 1 GB = 1024 MB and 1 MB = 8 megabits).
• Duration (min) – the total length of the video in minutes.
• Bitrate (Mbps) – the average data rate of the video stream, in megabits per second. This is the number you set in your encoder.

To convert from bitrate to file size, invert the formula:

File Size (GB) = (Bitrate in Mbps × Duration in seconds) / 8192

Remember that these formulas give the total bitrate (video + audio). If you are encoding audio separately, subtract the audio bitrate from the total to get the video bitrate.

Worked Example

Using the default values from the calculator: a 1080p video, 30 fps, 60 minutes long, with a target file size of 2 GB.

1. Convert file size to megabits: 2 GB × 8192 = 16384 megabits.
2. Convert duration to seconds: 60 min × 60 = 3600 seconds.
3. Divide: 16384 / 3600 = 4.5511 Mbps.
4. Rounded to two decimals: 4.55 Mbps.

So to fit a 60-minute 1080p video into 2 GB, you need an average bitrate of about 4.55 Mbps. The calculator also shows the file size at that bitrate (2 GB, confirming the round trip).

Why HEVC Bitrate Differs from H.264

HEVC (High Efficiency Video Coding, also called H.265) is the successor to H.264 (AVC). Its main advantage is that it can deliver the same visual quality at roughly 50–60% of the bitrate of H.264. For example, a 1080p video that needs 8 Mbps with H.264 might only need 4–5 Mbps with HEVC. This makes HEVC ideal for 4K and HDR content, where file sizes balloon with older codecs.

However, HEVC is more computationally demanding to encode and decode. Older devices may not support hardware decoding, causing playback stutter. Also, HEVC has licensing complexities, but for personal use this rarely matters.

How to Choose a Bitrate for HEVC

There are two common approaches:

• Target file size: If you know how large the output file should be (e.g., to fit on a USB stick or a streaming limit), use the calculator above. It gives you the average bitrate to set.
• Target quality (constant quality / CRF): Instead of a fixed bitrate, you let the encoder decide how many bits to use per frame to maintain a quality level. In x265 (the common HEVC encoder), a CRF value of 23–28 is typical. Lower numbers mean higher quality and larger files. This method is often better because it allocates more bits to complex scenes and fewer to simple ones.

For a rough guide, here are typical HEVC bitrates for common resolutions (assuming 30 fps, SDR content):

• 1080p: 2–5 Mbps
• 1440p (2K): 5–10 Mbps
• 4K: 10–20 Mbps

These are just starting points; adjust based on content type (fast action needs more) and your personal quality tolerance.

Common Mistakes and Misconceptions

One frequent error is mixing up megabits (Mb) and megabytes (MB). A bitrate of 8 Mbps equals 1 MB per second, not 8 MB. Always divide by 8 when converting to bytes.

Another mistake is ignoring audio bitrate. If you set the total bitrate to 4.55 Mbps and your audio track is 320 kbps (0.32 Mbps), the video bitrate is only 4.23 Mbps. For accurate file size prediction, subtract the audio bitrate from the total.

Also, the formula above gives the average bitrate. Actual encoding may use variable bitrate (VBR) with peaks higher than the average. If your target file size is a hard limit, use a two-pass encode or a constrained VBR to avoid overshooting.

Finally, don’t assume that doubling resolution requires doubling bitrate. Because of how human vision works, 4K needs only about 1.5–2× the bitrate of 1080p, not 4×, when using a modern codec like HEVC.

Limitations of the Calculator

This calculator gives you a mathematical average bitrate based on file size and duration. It does not account for:

• Content complexity: A static slideshow encodes well at low bitrates, while action scenes with noise require more.
• Resolution and frame rate: Higher resolutions and frame rates need more bits per second for the same quality. The calculator does not factor these in because it only uses file size and duration.
• Color depth and HDR: 10-bit HDR content needs more bitrate than 8-bit SDR for the same quality.
• Encoder efficiency: Different encoders (x265, NVENC, QuickSync) have different efficiencies. The calculator assumes a generic average.

For best results, use the calculator to get a starting bitrate, then do a short test encode (e.g., 1 minute of representative footage) and check the quality and file size before committing to a long encode.

Frequently Asked Questions

What is a good bitrate for 4K HEVC?

For 4K (3840×2160) HEVC at 30 fps, a bitrate of 15–20 Mbps is a good starting point for standard dynamic range content. For HDR or 60 fps, you may need 25–35 Mbps. For action-heavy content, go higher; for talking heads, you can go lower.

Is HEVC worth it over H.264?

Yes, if you need to save space or bandwidth and your playback devices support HEVC. You can typically halve the bitrate compared to H.264 for the same quality. However, encoding takes longer, and older devices may not play HEVC smoothly.

How do I calculate bitrate for a specific file size?

Use the formula: Bitrate (Mbps) = (File Size in GB × 8192) / (Duration in seconds). For example, a 90-minute movie in a 4.7 GB DVD-R would be (4.7 × 8192) / (5400) = 7.13 Mbps. Subtract audio bitrate for video-only.

What is CRF in x265 and what value should I use?

CRF (Constant Rate Factor) is a quality-based encoding mode. Lower values give higher quality and larger files. For x265, a CRF of 23–28 is a good range for 1080p; for 4K, you can use 25–30 because higher resolution hides artifacts. Test with your content to find the sweet spot.

Does resolution affect bitrate linearly?

No. Doubling resolution (e.g., from 1080p to 4K) increases the number of pixels by 4×, but the bitrate needed for the same perceived quality only increases by about 1.5–2×. This is because the human eye is less sensitive to fine detail at higher resolutions, and compression algorithms become more efficient.

Can I use the same bitrate for HDR as SDR?

HDR content generally needs a higher bitrate than SDR to avoid banding and preserve highlight detail. A good rule of thumb is to add 20–30% to the SDR bitrate for the same resolution and frame rate. For example, if SDR 4K needs 15 Mbps, HDR might need 18–20 Mbps.

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in res | Resolution | - | 1920x1080 | 0
in fps | Frame rate | fps | 30 | 0
in dur | Duration | min | 60 | 0
in size | Target file size | GB | 2 | 0
out bitrate | Required bitrate | Mbps | (size * 8192) / (dur * 60) | 2
out size_mb | File size at bitrate | MB | (bitrate * dur * 60) / 8 | 2