BitTorrent Peer Swarm & Port Forwarding Bandwidth Calculator (2026)

Without an open forwarded port, your client can only connect to peers who have open ports. When both peers have closed ports, they cannot connect, reducing your available swarm by up to 50%.

Use ephemeral ports between 49152 and 65535. Avoid legacy default port 6881–6889, which many ISPs throttle automatically.

On high-speed connections (300Mbps+), incoming random torrent pieces overwhelm the disk write queue. Increasing the RAM write cache (e.g., to 512MB or 1024MB) resolves this.

A swarm with high seeders (e.g. 50 seeders, 10 leechers) has surplus bandwidth, allowing you to max out your connection. Swarms with more leechers than seeders suffer bottlenecked upload speeds.

Yes! Set your upload limit to 80% of your ISP's max upload speed. Saturating 100% of your upload buffer chokes the TCP ACK packets required for fast downloads.