Formula Used
TotalBitrate(kbps) = CoreBitrate × VBRFactor × (1 + Overhead%) × (1 + Buffer%)
Size(bytes) = TotalBitrate(kbps) × 1000 × Duration(seconds) ÷ 8
How to Use This Calculator
- Enter duration in HH:MM:SS, MM:SS, or seconds.
- Set video and audio bitrates based on your encoding ladder.
- Pick delivery method to apply a typical packaging overhead.
- Adjust VBR factor if your streams fluctuate above the target.
- Add a safety buffer for ads, metadata, or peak complexity.
- Press Calculate to view size, per-hour usage, and exports.
Example Data Table
| Scenario | Duration | Video | Audio | Method | Overhead | VBR | Buffer | Estimated size |
|---|---|---|---|---|---|---|---|---|
| Mobile VOD | 00:30:00 | 1800 kbps | 128 kbps ×1 | HLS | 8% | 1.05 | 5% | ~0.46–0.55 GB |
| HD Episode | 00:45:00 | 4500 kbps | 192 kbps ×2 | DASH | 6% | 1.08 | 7% | ~1.75–2.10 GB |
| Live Event | 02:00:00 | 6000 kbps | 160 kbps ×1 | RTMP | 4% | 1.12 | 10% | ~6.0–7.2 GB |
Bitrate and duration drive predictable sizes
Streaming size starts with a simple relationship: bits per second multiplied by seconds. The calculator converts your video bitrate and audio bitrate to total kilobits per second, multiplies by the entered duration, then converts to megabytes or gigabytes. This is the same logic used when estimating CDN egress, cloud storage, or on-device caching targets.
Container and protocol overhead is not a rounding error
HLS, DASH, and RTMP introduce overhead through segment headers, manifests, and container metadata. Short segments improve switching and latency, but increase header density and playlist churn. The overhead presets in the tool provide practical starting points, while the custom option helps you model your encoder, muxer, and segment duration choices. For live workflows, consider extra playlist updates and discontinuity tags when you estimate overhead.
Adaptive ladders multiply cost across renditions
Most services publish multiple renditions for ABR playback. The ladder multiplier lets you approximate total output size when you store several bitrates for the same title. For example, keeping 240p through 1080p can easily double or triple storage compared with a single mezzanine. Use the multiplier to align packaging strategy with your catalog scale. If you store both CMAF and legacy formats, treat that as an additional multiplier or overhead increase.
Audio tracks, captions, and extras add up at scale
Audio is often smaller than video, yet multiple tracks—stereo, 5.1, commentary, and language dubs—compound quickly. Optional subtitle bandwidth models embedded or sidecar caption payloads. When you plan a global release, include tracks early so your storage and delivery projections match licensing and localization realities. The tool also supports multi-track audio so you can compare one-language previews versus full launch bundles.
Buffer and safety margins protect real-world planning
Real encodes vary with content complexity, scene cuts, and rate-control behavior. Network buffering, CDN chunking, and analytics beacons can add additional bytes. The buffer percentage in this calculator lets you build a conservative estimate for procurement and monitoring. Pair the result with samples from recent encodes to refine assumptions. Over time, track variance by genre and length so you can tighten margins without risking budget surprises.
FAQs
What does the calculator output represent?
It estimates the total bytes produced or delivered for a stream using your selected bitrates, duration, overhead, ladder multiplier, and buffer. Treat it as a planning figure, not a guarantee, because encoders and packaging settings can vary.
Should I use 1000 or 1024 for conversions?
Use 1000 for decimal marketing sizes and most network-rate discussions. Use 1024 for binary units commonly reported by operating systems and some storage tools. The calculator supports both so you can match your reporting standard.
How do I choose an overhead preset?
Start with the protocol you package for, then validate against a small exported sample. If your segment duration is very short, overhead usually increases. Use the custom overhead option when you have measured data from your pipeline.
How do I model multiple renditions accurately?
Add the sizes of each rendition separately for best precision. If you need a quick estimate, set the ladder multiplier to the number of renditions and keep the overhead consistent. Adjust upward if you store multiple container variants.
Does live streaming differ from VOD sizing?
The math is similar, but live may include extra playlist updates, discontinuities, and slightly higher padding for resilience. Also consider DVR windows and retained segments, which can turn a live event into a sizable temporary storage footprint.
Why include a buffer percentage?
Buffer accounts for bitrate variability, additional tracks, tracking beacons, and operational safety margin. It helps procurement and capacity plans survive real-world variance. If you have historical encode metrics, tune the buffer to match observed overages.