Why does 1 GB take longer than eight seconds at 1 Gbps?

A decimal gigabyte contains eight gigabits, so the theoretical minimum is eight seconds before efficiency losses and other bottlenecks.

What is effective throughput?

It is the portion of nominal link speed available to the file after protocol and real-world efficiency losses.

What is bandwidth-delay product?

It is bandwidth multiplied by round-trip time, representing how much data must be in flight to fill the path.

Is this a network speed test?

No. The calculator uses values you enter and makes no network request.

File Transfer Time & Bandwidth Calculator

Estimate transfer time from file size, link speed, efficiency, and RTT, including bandwidth-delay product.

Local browser processing

Addresses and calculation inputs stay in this browser. They are not uploaded, resolved, scanned, or sent to analytics.

File size

Unit

Link speed

Unit

Mbps

Effective throughput

Round-trip time

Result

Enter values and run the tool to see the local result.

How file-transfer time is estimated

Transfer time equals file bits divided by effective bits per second. This calculator keeps decimal and binary size units explicit, applies your throughput-efficiency percentage, and uses optional round-trip time to estimate the bandwidth-delay product needed to keep the link busy.

How to estimate transfer time

Enter the file size and choose its decimal or binary unit.
Enter link speed, effective-throughput percentage, and optional round-trip time.
Review the estimated duration, effective rate, and bandwidth-delay product.

Why real transfers may differ

The result is arithmetic, not a live speed test. Real performance also depends on congestion, latency behavior, retransmissions, protocol overhead, Wi-Fi, storage, server limits, and parallel connections.

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Transfer-time questions

Why does 1 GB take longer than eight seconds at 1 Gbps?: A decimal gigabyte contains eight gigabits, so the theoretical minimum is eight seconds before efficiency losses and other bottlenecks.
What is effective throughput?: It is the portion of nominal link speed available to the file after protocol and real-world efficiency losses.
What is bandwidth-delay product?: It is bandwidth multiplied by round-trip time, representing how much data must be in flight to fill the path.
Is this a network speed test?: No. The calculator uses values you enter and makes no network request.