A/B Testing Video Bitrate Annual Cost Formula
Learn how to calculate annual video bandwidth transfer and CDN cost differences between a control bitrate and a test bitrate.
This calculation estimates how a change in average delivered video bitrate affects annual data transfer and CDN delivery cost. It converts watch time into data used per play, scales that amount by annual video plays, and compares the control and test versions.
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Estimated Annual CDN Cost Savings
Where:
Find the bitrate difference, convert the watched video data from megabits to megabytes, multiply it by yearly plays, convert megabytes to GB, and multiply by the CDN price per GB. A positive result means the test version is estimated to cost less to deliver.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| controlBitrate - Control bitrate | Average delivered bitrate for the current or control video version. | Mbps |
| testBitrate - Test bitrate | Average delivered bitrate for the A/B test video version. | Mbps |
| averageWatchTime - Average watch time | Average amount of video watched during one play. | minutes |
| monthlyVideoPlays - Monthly video plays | Expected number of complete and partial video plays in a typical month. | number |
| cdnCostPerGb - CDN cost per GB | Average cost charged for each GB of delivered video data. | currency |
Step-by-Step Calculation
Convert average watch time to seconds
Video bitrates are measured per second, so watch time in minutes must first be converted to seconds.
watchTimeSeconds = averageWatchTime * 60
Estimate annual video plays
The calculation assumes the entered monthly play volume remains the same for 12 months.
annualVideoPlays = monthlyVideoPlays * 12
Calculate control data per play
Multiplying Mbps by seconds gives megabits. Dividing by 8 converts megabits to megabytes.
controlDataPerPlayMb = controlBitrate * watchTimeSeconds / 8
Calculate test data per play
The same conversion is applied to the test bitrate and average watch time.
testDataPerPlayMb = testBitrate * watchTimeSeconds / 8
Calculate annual transfer difference
The per-play difference is multiplied by annual plays and converted from MB to GB using decimal units.
annualDataSavedGb = (controlDataPerPlayMb - testDataPerPlayMb) * annualVideoPlays / 1000
Calculate annual CDN cost difference
The annual transfer difference is multiplied by the entered average CDN delivery price.
annualCostSavings = annualDataSavedGb * cdnCostPerGb
Example: Reducing bitrate from 5 Mbps to 3.5 Mbps
Convert watch time
4 * 60
240 seconds
Calculate annual plays
100,000 * 12
1,200,000 plays
Calculate control data per play
5 * 240 / 8
150 MB per play
Calculate test data per play
3.5 * 240 / 8
105 MB per play
Calculate annual transfer saved
(150 - 105) * 1,200,000 / 1,000
54,000 GB
Calculate annual CDN savings
54,000 * 0.05
$2,700
Final Result
The 3.5 Mbps test bitrate is estimated to save 54,000 GB of annual transfer and $2,700 in annual CDN delivery cost versus the 5 Mbps control.
Assumptions
- ✓Average watch time is representative of actual viewing behavior for both video versions.
- ✓Monthly video plays remain consistent throughout the 12-month estimate.
- ✓The bitrate entered represents the average delivered bitrate for the relevant audience and device mix.
- ✓The calculation uses decimal data units: 1,000 MB equals 1 GB.
- ✓The CDN cost per GB stays unchanged during the year.
Limitations
- !Actual CDN invoices can vary by region, pricing tier, committed-use agreement, traffic mix, and billing rules.
- !The estimate does not separately model audio, manifests, request charges, protocol overhead, retries, or cache behavior unless they are included in the entered bitrate or blended cost.
- !A bitrate change can affect video quality, buffering, completion rate, and conversion outcomes, which are not priced by this formula.
- !Monthly plays and watch time may be seasonal rather than constant.
Common Mistakes to Avoid
Entering a video file's maximum encoding bitrate instead of the average bitrate actually delivered to viewers.
Using total video length when viewers typically watch only part of each video.
Entering a CDN price in cents as though it were a currency amount; for five cents per GB, enter 0.05.
Mixing binary and decimal transfer units when comparing the result with provider reports.
Treating a negative savings result as an error; it means the test bitrate is higher and is estimated to use more data.
Selecting a bitrate only on delivery cost without reviewing experiment results for viewing quality and engagement.
Related Formulas
Frequently Asked Questions
How is annual video bandwidth calculated from bitrate?
The calculator multiplies bitrate in Mbps by average watch time in seconds, divides by 8 to get MB per play, multiplies by annual plays, then divides by 1,000 to get GB.
Why does the formula divide bitrate by 8?
Bitrate is measured in megabits per second, while transfer is expressed in megabytes or GB. There are 8 bits in 1 byte.
What does a negative annual cost savings result mean?
It means the test bitrate is higher than the control bitrate, so the test is estimated to use more data and cost more to deliver.
Does video duration affect the annual bitrate cost calculation?
It affects costs only through average watch time. If viewers watch less than the full duration, average watch time is generally the more relevant input.
Can I include audio in the bitrate calculation?
Yes. Use a total average delivered bitrate that includes video, audio, and any overhead you want reflected in the estimate.
Is 1 GB equal to 1,000 MB in this calculator?
Yes. The calculation uses decimal transfer units, where 1,000 MB equals 1 GB.
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