Data Transfer Calculator
Estimate transfer time based on file size, port speed, and protocol efficiency.
Most port-speed numbers are marketing numbers, not transfer numbers. A "10 Gigabit" connection doesn't actually move 10 gigabits of usable data every second — protocol overhead, error checking, and real-world network conditions all take a cut. This calculator accounts for that gap.
Pick a file size, a port speed, and a protocol efficiency setting that matches your actual conditions — congested, typical, or ideal — and you'll get a transfer time that's much closer to what you'd see in practice than a naive "file size ÷ port speed" estimate. It works the same way whether you're estimating a local file transfer, a NAS backup, or a full data migration between drives or systems — the underlying math is identical no matter what you call the use case.
Port Speed
Select a port speed to see the estimate.
Frequently Asked Questions
How is data transfer time calculated?
Transfer time is the file size divided by the effective throughput of the connection. Effective throughput is usually lower than the advertised port speed because of protocol overhead, so this calculator factors in a protocol efficiency percentage on top of the raw port speed to give a more realistic estimate.
Why is my actual transfer speed slower than my port speed?
No connection runs at 100% of its rated speed in practice. Protocol overhead, error checking, and network conditions all take a cut. A "typical" real-world connection runs at roughly 85% efficiency, while a congested or older connection can drop closer to 50%. That's why this calculator includes a protocol efficiency slider instead of just dividing file size by port speed.
What's the difference between a data transfer calculator and a data migration calculator?
They're answering the same underlying question — how long will it take to move a given amount of data over a connection of a given speed — just applied to different contexts. "Data transfer" usually refers to moving files between two devices on a local network, while "data migration" often refers to moving data between systems, drives, or platforms (like switching NAS units or cloud providers). The math is identical; this calculator works for both.
Does this calculator account for real-world network conditions?
Yes, through the protocol efficiency setting. Selecting "50% congested" models a busy or contended network, "85% typical" reflects normal day-to-day conditions, and "98% ideal" reflects a clean, dedicated, low-latency connection — useful for comparing best-case vs. realistic-case transfer times on the same port speed.
How long does it take to transfer 1TB over 10GbE?
At the "typical" 85% protocol efficiency setting, a 1TB transfer over a 10GbE (10 Gbps) connection takes about 15 minutes and 41 seconds. The exact number depends on the protocol efficiency you select — use the calculator above for an exact figure at any combination of size, port speed, and efficiency.