File Transfer Time Calculator

Not every large file transfer goes over the internet. Copying files to an external drive, moving a media library across a home network, or transferring data between two computers on the same LAN all have their own speed characteristics, often very different from internet download speeds. This calculator estimates transfer time across any of these connection types.

What the Result Means

Enter the size of the data you’re moving, then pick the interface carrying it — USB 2.0 through USB 3.2 Gen 2×2, internal SATA or NVMe (PCIe 3.0/4.0), or 1/2.5/10 Gigabit Ethernet — or enter a custom speed for Wi-Fi or a speed you’ve measured yourself, and the calculator estimates how long the transfer should take. Unlike an internet download, many of these transfer types are capable of far higher sustained speeds, which changes the practical planning question from “will this take all evening” to “will this take a few minutes or a few seconds.”

This is especially useful for figuring out realistic timing for large jobs like transferring a full photo or video library to a new external drive, migrating files between two computers over a local network, or backing up a NAS.

How This Calculator Works

Choose the connection carrying your data from the dropdown — each preset uses that interface’s real sustained throughput after protocol overhead, not its raw marketing number:

• USB 2.0 (480 Mbps): ~53MB/s interface maximum.
• USB 3.2 Gen 1 / USB 3.0 (5 Gbps): ~500MB/s.
• USB 3.2 Gen 2 (10 Gbps): ~1,212MB/s.
• USB 3.2 Gen 2×2 (20 Gbps): ~2,424MB/s.
• SATA III internal (6 Gbps): ~600MB/s — the standard figure for internal SATA SSDs and HDDs.
• NVMe on PCIe 3.0 x4: ~3,938MB/s.
• NVMe on PCIe 4.0 x4: ~7,877MB/s.
• Gigabit Ethernet (1 Gbps): ~125MB/s.
• 2.5 Gigabit Ethernet: ~313MB/s.
• 10 Gigabit Ethernet: ~1,250MB/s.
• Custom speed: for Wi-Fi or any measured speed not in the list above — enter it directly in MB/s, Mbps, or Gbps.

Then pick a real-world factor: 100% (theoretical maximum, rarely sustained), ~80% (typical for one large file copy), or ~50% (many small files, or a link shared with other traffic). This is what turns an interface’s ceiling into a realistic estimate — an “up to” USB or Wi-Fi speed rarely holds for an entire large copy.

Worked example: copying a 500GB media library over USB 3.2 Gen 2 (10 Gbps), at the “typical large-file copy” (~80%) real-world factor:

• Interface maximum: 1,212MB/s
• At 80%: 1,212 × 0.8 ≈ 970MB/s sustained
• 500,000MB ÷ 970MB/s ≈ 515 seconds ≈ 8 minutes 36 seconds

Switch that same transfer to Gigabit Ethernet instead and the estimate jumps to around 83 minutes — the interface you pick changes the answer far more than fine-tuning the real-world factor does.

Important Limitations

• The slowest link in the chain sets the pace. A fast network means little if the source or destination drive itself is the bottleneck — an older mechanical hard drive can cap a transfer well below what the network connection could otherwise support.
• Many small files transfer slower than one large file of the same total size. File-system overhead per file (especially over Wi-Fi or network shares) adds up, so a folder of thousands of small files often takes noticeably longer than a single large archive of equal size.
• Wi-Fi speed is highly situational. Distance from the router, interference, the number of other connected devices, and the Wi-Fi standard in use all affect real throughput, sometimes dramatically.
• Advertised interface speeds (like USB 3.0’s “5 Gbps”) are ceilings, not typical results. Real-world sustained speed is usually well below the interface’s theoretical maximum, particularly for USB flash drives and SD cards.