What is the Bandwidth-Delay Product (BDP)?

BDP represents the amount of data that can be 'in flight' on a network path at any time. It's calculated as bandwidth × RTT. For example, a 100 Mbps link with 100ms RTT has a BDP of 1.25 MB. Your TCP window must be at least this size to fully utilize the link.

How does packet loss affect TCP throughput?

Packet loss has a severe impact on TCP throughput. The Mathis formula shows that throughput is inversely proportional to the square root of packet loss. Even 1% loss can reduce throughput by 90% on high-speed links. This is why lossy networks feel much slower than the bandwidth suggests.

What is TCP Window Scaling?

Window Scaling (RFC 1323) allows TCP windows larger than 64KB. Without it, the maximum window is 65,535 bytes, limiting throughput on high-BDP links. Modern operating systems enable this by default. With scaling, windows up to 1GB are possible.

How do I measure RTT for my connection?

Use the ping command to your destination server: 'ping example.com'. The reported time is the RTT. For more accurate measurements, use multiple samples and take the average. Tools like mtr or pathping show RTT at each hop.

What is a good TCP window size?

The optimal window size equals or exceeds your BDP. For a 100 Mbps link with 50ms RTT, you need at least 625 KB. For most modern internet connections, enabling TCP window scaling and letting the OS auto-tune is sufficient. Manual tuning may help for specialized applications.

Technology

TCP Throughput Calculator

Optimize network performance by calculating TCP throughput limits. Analyze bandwidth-delay product, window size efficiency, and packet loss impact using industry-standard formulas.

Link Bandwidth

Bandwidth Unit

Round-Trip Time (RTT)

Advanced Parameters (Optional)

TCP Window Size

bytes

Packet Loss

Maximum Segment Size

bytes

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Calculate Your Network's TCP Throughput

TCP throughput determines how fast data can actually flow through your network connection. It's not just about bandwidth - factors like round-trip time (RTT), TCP window size, and packet loss significantly impact real-world performance. This calculator helps you understand and optimize your network's effective throughput.

Understanding TCP Throughput

TCP throughput is the effective data transfer rate achieved by the TCP protocol. While your link bandwidth defines the maximum possible speed, TCP's reliability mechanisms (acknowledgments, flow control, congestion control) often limit actual throughput. The Bandwidth-Delay Product (BDP) determines how much data can be 'in flight' at any time.

Bandwidth-Delay Product

BDP = Bandwidth (bytes/sec) × RTT (seconds)

Why Calculate TCP Throughput?

Diagnose Performance Issues

Identify whether slow transfers are caused by insufficient bandwidth, high latency, or incorrect TCP settings.

Optimize Window Size

Determine the optimal TCP window size for your connection to maximize throughput without wasting resources.

Plan Network Upgrades

Understand whether upgrading bandwidth will actually improve performance or if TCP tuning is needed first.

Troubleshoot VPN Performance

VPN connections often suffer from TCP overhead and suboptimal settings - calculate expected throughput accurately.

How to Calculate TCP Throughput

Common Use Cases

Long-Distance File Transfers

Calculate achievable speeds for transcontinental data replication and backup operations.

Cloud Migration Planning

Estimate data migration times based on realistic TCP throughput to cloud providers.

WAN Optimization

Determine whether WAN accelerators or TCP tuning can improve branch office performance.

Video Streaming Capacity

Verify if your connection can sustain required bitrates for video conferencing or streaming.

Frequently Asked Questions

TCP throughput is limited by the Bandwidth-Delay Product (BDP). If your TCP window size is smaller than the BDP, you can't fully utilize your bandwidth. High RTT connections need larger windows. Additionally, packet loss dramatically reduces throughput due to TCP's congestion control algorithms.

Calculate Your Network's TCP Throughput

Understanding TCP Throughput

Bandwidth-Delay Product

BDP = Bandwidth (bytes/sec) × RTT (seconds)