Caption and Subtitle Character Count Design Guide
Captions and subtitles serve different purposes—from making video content accessible to enhancing social media engagement—but they share a common challenge: conveying meaning within tight character constraints. Netflix's subtitle guidelines recommend a maximum of 42 characters per line, while Instagram captions can stretch to 2,200 characters. This guide covers character count best practices for every caption and subtitle format.
Video Subtitle Standards
| Platform / Standard | Max Chars per Line | Max Lines | Display Duration |
|---|---|---|---|
| Netflix (Timed Text) | 42 chars | 2 lines | Min 0.833s, max 7s |
| BBC Subtitle Guidelines | 37 chars | 2 lines | Min 1.5s per line |
| YouTube Auto-captions | 32 chars | 2 lines | Varies by speech rate |
| DVD / Blu-ray | 40 chars | 2 lines | Min 1s, max 6s |
| Cinema (DCP) | 40 chars | 2 lines | Min 1s, max 5s |
The reading speed assumption for subtitles is 150–200 words per minute (roughly 12–17 characters per second). Exceeding this forces viewers to choose between reading and watching the visuals.
Social Media Caption Lengths
| Platform | Max Length | Optimal Length | Truncation Point |
|---|---|---|---|
| 2,200 chars | 125–150 chars | 125 chars (before "more") | |
| 63,206 chars | 40–80 chars | 477 chars (before "See more") | |
| TikTok | 4,000 chars | 50–150 chars | ~55 chars visible without tap |
| 3,000 chars | 100–150 chars | 140 chars (before "see more") | |
| 500 chars | 100–200 chars | ~75 chars in feed |
Image Caption Guidelines
- News photography: 15–30 words. Include who, what, where, when. Attribution and date are mandatory
- Museum / gallery labels: 50–100 words. Artist, title, medium, year, plus brief interpretive text
- Scientific figures: 25–75 words. Describe what the figure shows and highlight key findings
- Alt text (accessibility): 50–125 characters. Describe the image content for screen readers; avoid "image of" or "photo of"
- Product photos: 10–25 words. Feature name, key benefit, or use case
Subtitle Timing and Readability
- Minimum display time: 1 second for short phrases, 1.5 seconds per line for full sentences
- Maximum display time: 7 seconds. Longer durations cause viewers to re-read unnecessarily
- Line breaks: Break at natural linguistic boundaries—after conjunctions, before prepositions. Never split a proper noun across lines
- Reading speed: Adults read subtitles at 150–200 WPM. Children's content should target 120–150 WPM
- Speaker identification: Use color coding or name labels when multiple speakers overlap, adding 5–15 characters per subtitle
Accessibility Considerations
- Closed captions vs. subtitles: Captions include sound effects and speaker IDs (adding 10–30 chars per line); subtitles are dialogue only
- Font size: Minimum 22px for standard video, 28px for mobile-first content
- Contrast: White text on a semi-transparent black background ensures readability across all scenes
- Positioning: Bottom-center by default; move to top when lower-third graphics or important visual elements appear
Conclusion
Video subtitles should stay under 42 characters per line with a maximum of 2 lines displayed for up to 7 seconds. Social media captions perform best when the key message fits before the truncation point—125 characters on Instagram, 40–80 on Facebook. For accessibility, always provide closed captions with sound descriptions. Use Character Counter to verify your caption and subtitle lengths.