Calculator
Example Data Table
| Rendition | Video (kbps) | Audio (kbps) | Overhead (%) | Segment (s) | Total (approx Mbps) |
|---|---|---|---|---|---|
| 1080p | 5000 | 128 | 6 | 6 | 5.436 |
| 720p | 2800 | 128 | 6 | 6 | 3.104 |
| 480p | 1400 | 96 | 6 | 6 | 1.584 |
Formula Used
- Payload bitrate (kbps) = Video kbps + Audio kbps + Captions kbps
- Total bitrate (kbps) = Payload kbps × (1 + Overhead% / 100)
- Total bitrate (Mbps) = Total kbps ÷ 1000
- Segment size (MB) = (Total kbps × Segment seconds) ÷ 8 ÷ 1024
- GB per hour per viewer = ((Total kbps × 1000) ÷ 8 × 3600) ÷ 1,000,000,000
- Estimated total GB = Weighted GB/hour/viewer × Hours × Viewers
- Estimated cost = Total GB × Price per GB
How to Use This Calculator
- Enter your segment duration and expected viewing time.
- Add each rendition and input video, audio, and captions bitrates.
- Set overhead to account for packaging, encryption, and requests.
- Optionally add traffic share percentages to reflect real usage.
- Add viewers and a per‑GB price to estimate transfer and cost.
- Click Calculate to see summary metrics and the rendition table.
- Use CSV or PDF export to share results with your team.
Insights
Bitrate budgeting
HLS bitrate planning starts with a realistic video budget per resolution and frame rate, then adds audio and other tracks. For most ladders, the top rendition defines the worst‑case peak bandwidth, while the mix of renditions defines the average delivery footprint. Use the overhead field to cover packaging, encryption, playlist fetches, and protocol chatter. A 5–10% overhead range is common when manifests are cached and segments are sized well. Document assumptions and revisit them carefully each quarter.
Segment size signals
Segment size influences latency, cache efficiency, and request pressure. Smaller segments reduce glass‑to‑glass delay but increase HTTP requests per viewer, which can raise overhead and origin load. Larger segments improve throughput and reduce request counts, but can slow bitrate switching and increase rebuffer risk on volatile networks. Align segment duration with your player targets, CDN tuning, and encoder GOP structure for stable switching behavior.
Traffic share modeling
Traffic shares turn a ladder into a forecast. If you have analytics, enter the percentage of playback time spent at each rendition to compute a weighted average bitrate. Without shares, the calculator evenly averages, which may understate costs for audiences that skew high resolution. Shares also help you evaluate ladder changes, such as adding a 360p safety rung for mobile, or tightening the 1080p bitrate to reduce egress spend.
Transfer and cost
Data transfer scales linearly with time and viewers, so a small bitrate change can be expensive at scale. The calculator converts bitrate into GB per hour per viewer, then multiplies by viewing hours and average concurrent viewers. Compare the resulting GB to your CDN billing units and ensure you apply the correct rate for region, commitment tiers, and cache hit ratios. For events, model multiple viewer phases to avoid surprises.
Quality guardrails
Bitrate is only one dimension of quality. Keep codecs, profiles, and level constraints consistent across renditions so the player can switch cleanly. Validate that audio is appropriate for content type, and account for captions or timed metadata if you deliver them. After you compute the ladder, test on constrained networks, confirm ABR behavior, and measure rebuffering, startup time, and visual quality to refine targets over time.
FAQs
What bitrate should I put in the video field?
Use the encoder target video bitrate for that rendition, expressed in kbps. If you have a range, enter the typical sustained value, not a brief peak.
Why does overhead matter for HLS delivery?
Beyond media bytes, delivery includes playlists, encryption, headers, retries, and player behavior. Overhead lets you approximate those extras so bandwidth and transfer estimates match reality better.
How do traffic shares improve the estimate?
Shares weight each rendition by how often viewers actually watch it. That produces a more realistic average bitrate and transfer total than evenly averaging all renditions.
Is segment size calculated for TS and fMP4?
Yes. The segment size is based on bitrate and duration, so it applies to either container. Packaging format can slightly change overhead, which you can reflect in the overhead percentage.
How do I estimate peak bandwidth for a live event?
Set viewers to your expected peak concurrency. Peak worst‑case assumes everyone pulls the highest rendition, which is conservative; combine it with traffic shares for an expected average.
Can this replace CDN billing reports?
No. It is a planning model. Use it to compare ladders and scenarios, then validate against your CDN analytics, cache hit ratio, and region pricing to finalize budgets.