The short answer? It depends on what kind of post you are posting. Below you will find the recommendations, based on the Algorithm Insights Report 2025.
Text-Only Posts
Best performance at 1000+ characters (≈300–400 words)
Avoid <100 words (–50% engagement)
Posts with 20+ sentences perform best for dwell time
Text + Image Posts
700–900 characters is the sweet spot
Captions with 400+ words (20+ sentences) can drive 2.3x engagement
Under 100 words = weak engagement (0.71x)
Over 1000 characters: no significant reach gain
Document (PDF/Carousel) Posts
Short captions (<100 characters) drive highest engagement .
Captions >800 characters hurt performance (–7% per +400 chars) .
Mid-length: 200–300 words works best when more context needed .
Structure: either very short (0–5 sentences) or long (20+ sentences) – middle length underperforms
Poll Posts
Polls with 1000+ characters in the description generate highest engagement (esp. company pages)
Strongest when framed with a short hook + context (1–2 lines)
3 answer options perform best
Engagement boosted by 20+ sentences in body for background/context
Video Posts
Short-form: 30–90 sec dominates feeds
Sweet spot: 1–2 minutes → +60% higher interaction, +30% better conversion
Videos >3 minutes: –30% engagement drop
No strict caption length rule, but hooks in first 3 seconds and concise supporting text matter most
Summary:
Format | Optimal Caption Length | Notes |
Text-only | 1000+ characters (300–400 words) | Best for depth, thought leadership |
Text + Image | 700–900 characters | Visual + structured text = 2.3x engagement |
Document/Carousel | <100 characters (short) | If longer: 200–300 words; avoid 800+ |
Polls | 1000+ characters | Best when detailed + contextual |
Video | N/A (focus on 1–2 min runtime) | Caption = short hook + CTA |