What is the bandwidth-delay product?

BDP is the product of a link's bandwidth and its round-trip time (RTT). It represents the maximum amount of data that can be "in flight" on the network at one time — filling the pipe — before any acknowledgment returns.

Why does BDP matter for TCP performance?

TCP's throughput is capped at window_size / RTT. If your TCP send/receive buffers are smaller than the BDP, the pipe stays partially empty and you waste available bandwidth. Setting buffers to at least 1–2× BDP lets TCP fill the link.

Should I use one-way latency or RTT?

Use RTT (round-trip time) for TCP buffer sizing — a TCP ACK must travel the full round trip before the sender can refill the window. If you only know one-way latency (e.g. a ping result divided by 2), select "one-way" and the tool doubles it.

What is a typical recommended buffer size?

A common rule is to set the socket buffer (SO_SNDBUF / SO_RCVBUF) to at least 1× BDP. For high-jitter links, 2× BDP provides headroom. Linux auto-tuning (tcp_rmem / tcp_wmem) can handle this automatically if the max values are large enough.

Does a larger buffer always help?

No. Oversized buffers can cause buffer bloat — excessive queuing that increases latency without improving throughput. Aim for a buffer in the range of 1–2× BDP.

Bandwidth-Delay Product Calculator

Enter link bandwidth and round-trip time to calculate how much data fills the network pipe and get TCP send/receive buffer size recommendations.

Link Parameters

Quick Presets

Link Bandwidth

Latency (ms)

RTT = round-trip time (use for TCP). One-way is doubled internally.

Bandwidth-Delay Product

Enter bandwidth and latency to calculate BDP

TCP Buffer Recommendations

Results appear after calculation above.

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Summary

The bandwidth-delay product (BDP) quantifies how much data can be in transit on a network link at any moment. It equals link bandwidth multiplied by round-trip time. For TCP to fully utilize a link, the socket send and receive buffers must be at least as large as the BDP — otherwise the connection stalls waiting for acknowledgments before it can send more data. This calculator converts your link speed and RTT into a BDP figure and recommends appropriate buffer sizes.

How it works

Enter the link bandwidth (bits per second) — use the unit selector for Kbps, Mbps, or Gbps.
Enter the one-way latency or round-trip time (RTT) in milliseconds.
Choose whether you entered one-way latency or RTT — the calculator converts automatically.
The BDP appears instantly in bits, bytes, kilobytes, and megabytes.
Check the TCP buffer recommendation section to see the minimum socket buffer size needed.
Use the presets for common link types (LAN, WAN, satellite, etc.) as starting points.

Use cases

Size TCP socket buffers for high-throughput WAN or intercontinental links.
Estimate in-flight data for network capacity planning.
Debug slow file transfers over long-distance links.
Verify that TCP window size matches the pipe capacity.
Teaching networking concepts like pipe-filling and buffer bloat.
Compare link efficiency across different bandwidth and latency combinations.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu