Free Video Size Calculator: Predict File Size from Length & Bitrate

How to Use a Video Size Calculator to Plan Storage & Uploads

1) Gather the inputs

• Duration: total length in seconds or minutes.
• Resolution & frame rate: e.g., 1920×1080 at 30fps (affects encoder choice but not direct size calc).
• Bitrate: video bitrate (kbps or Mbps). If unknown, use typical values (e.g., 1080p ≈ 8–12 Mbps, 4K ≈ 25–50 Mbps).
• Audio bitrate: common values: 128–320 kbps.
• Container/overhead: small percentage (1–5%) for metadata, subtitles, etc.

2) Use the calculator formula

• Convert bitrates to bits per second: Mbps × 1,000,000 or kbps × 1,000.
• File size (bytes) ≈ (video_bitrate_bps + audio_bitrate_bps) × duration_seconds / 8.
• Add container overhead: total_bytes × 1.02–1.05.

Example: 10 Mbps video + 192 kbps audio, 5 minutes (300 s):

• Video = 10,000,000 × 300 = 3,000,000,000 bits
• Audio = 192,000 × 300 = 57,600,000 bits
• Total bits = 3,057,600,000 → bytes = /8 = 382,200,000 ≈ 382.2 MB (before overhead).
• With 3% overhead → ≈ 393.7 MB.

3) Plan storage and uploads

• Multiply per-file size by number of files and add headroom (20–30%) for versions/backsups.
• For uploads, estimate required bandwidth/time: upload_time_seconds = file_size_bytes × 8 / upload_speed_bps. Convert to minutes/hours.
• Consider network caps and parallel uploads; compress or lower bitrate to fit limits.

4) Tips to reduce size

• Lower bitrate or resolution.
• Use efficient codecs (HEVC/AV1) for smaller size at similar quality.
• Reduce frame rate if appropriate.
• Re-encode audio to lower bitrate or mono if acceptable.

5) Quick checklist before exporting

• Confirm target platform bitrate/format requirements.
• Run a short test clip to verify quality vs size.
• Keep a spreadsheet of presets and resulting file sizes for future planning.