Video File Size Calculator — Size from Bitrate & Duration
A video file size calculator estimates the finished size of a video from its average bitrate and running time — the number you need before exporting, uploading or budgeting storage for a shoot.
Quick answer: Size = bitrate × duration ÷ 8. One hour of 1080p60 H.264 at 8 Mbps is about 3.6 GB; one hour of 4K30 at 25 Mbps is about 11.3 GB, and the same 4K clip in H.265 is nearer 6.8 GB at matched quality.
Formats: 90m · 1h30m · 5400s · plain number = seconds
Typical H.264 average bitrates at medium quality
Overrides the preset when filled — use the target bitrate from your encoder settings
| Duration | Size (decimal GB/MB) |
|---|---|
| 1 min | 37.5 MB |
| 5 min | 187.5 MB |
| 30 min | 1.125 GB |
| 1 h | 2.25 GB |
| 2 h | 4.5 GB |
| 10 h | 22.5 GB |
| Formula | GB = Mbps × 3,600 ÷ 8,000 per hour (≈ 0.45 GB per Mbps-hour) |
|---|---|
| 1080p30 H.264 | ~5 Mbps → 2.25 GB per hour |
| 1080p60 H.264 | ~8 Mbps → 3.6 GB per hour |
| 4K30 H.264 | ~25 Mbps → 11.3 GB per hour |
| Codec effect | H.265 ≈ 0.6× and AV1 ≈ 0.5× the H.264 size at equal visual quality |
Bitrate is an average, not a constant
Encoders spend bits where the picture changes: a talking head at 8 Mbps average looks identical to a 3 Mbps average of the same scene, while a fireworks display will starve. That is why two “1080p” files can differ by 5× in size and both be correct. For planning, use the encoder's target bitrate (constant-quality modes report an average after the fact) and accept a ±20% range.
Choosing a bitrate for the destination
YouTube suggests 8 Mbps for 1080p SDR uploads, 16 Mbps for 1440p and 35–45 Mbps for 4K; Twitch wants about 6 Mbps for 1080p60 live. Editing codecs are a different world: ProRes 422 HQ at 1080p30 runs around 220 Mbps — about 100 GB per hour — because every frame is stored almost raw. Export a lightweight H.264 master for archiving and keep ProRes only for the edit bay.
Storage planning for shoots
A one-hour interview in 4K H.264 is about 11 GB; a full day of shooting (6 hours of footage) is 68 GB before backups, and the edit cache roughly doubles it. On a 512 GB laptop that means one project at a time — which is why editors push proxies (540p H.264 at 2 Mbps, 0.9 GB per hour) and keep the originals on external storage.
When to use this calculator
- Checking whether a finished video fits an upload size limit.
- Budgeting storage for a multi-day shoot or a live stream archive.
- Choosing between H.264, H.265 and AV1 exports for size vs compatibility.
- Planning how many hours of footage fit on an SD card or SSD.
- Estimating how long an export will take to upload.