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TCP Window Size Calculator

Calculate optimal TCP window size for maximum throughput based on bandwidth-delay product.

The bandwidth of the network link in Mbps. This is the raw link speed, e.g. 100, 1000, or 10000 Mbps.
Mbps
The time for a packet to travel to the destination and back. Typical LAN: 0.5-2ms, WAN same continent: 20-60ms, intercontinental: 100-300ms.
ms
The current configured TCP receive window size. Default is 65,535 bytes (64 KB) without window scaling. Modern OS may use larger values.
bytes

TCP Window Size Results

Bandwidth-Delay Product (BDP)-bytes
BDP-KB
Optimal Window Size-bytes
Window Scale Factor Needed-
Max Throughput (current window)-Mbps
Max Throughput (optimal window)-Mbps
Current Utilization-%
Throughput Improvement-x
References: RFC 1323 (TCP Window Scaling). RFC 793 (TCP). BDP = Bandwidth x RTT. Default TCP window: 65,535 bytes (16-bit field).