Does USB-C tell me the transfer speed?

No. USB-C describes the connector shape, not its data capability. A USB-C port or cable may carry USB 2.0, USB 5/10/20/40/80Gbps, Thunderbolt or another mode. The host, cable, dock or hub, enclosure and device negotiate to the slowest supported capability, so select the actual advertised or measured protocol.

Why does Thunderbolt 5 use 80 Gbps instead of 120 Gbps?

Thunderbolt 5 provides an 80 Gbps bidirectional base link and a 120/40 Gbps Bandwidth Boost mode intended for display-heavy traffic. Storage planning should use the 80 Gbps mode and the 64 Gbps PCIe data path rather than treating 120 Gbps as normal file-copy bandwidth.

Do Windows, macOS and Linux transfer at different speeds?

There is no defensible universal multiplier for an operating system. File system, drivers, copy software, antivirus or indexing, SMB or NFS settings, signing and encryption, CPU load, caching and file count matter more. The operating-system selector changes guidance only; it does not secretly alter the calculation.

How does the calculator handle NAS and DAS storage?

NAS and DAS describe how storage is attached, not a fixed speed. Enter the array's sustained read and write performance, then model the USB, Thunderbolt, Ethernet, Wi-Fi or fiber path separately. A NAS can be limited by its disks, RAID work, client and server NICs, switch uplink, protocol, CPU or destination drive.

Why can many small files take much longer?

Each file adds directory, permission, metadata and open/close work. Antivirus, checksums, network latency and hard-drive seeks can amplify that cost. The File Layout setting applies a visible planning efficiency, and archiving a folder before transferring it can sometimes improve throughput substantially.

What is the difference between GB and GiB?

GB is decimal: 1,000,000,000 bytes. GiB is binary: 1,073,741,824 bytes. A 100 GiB transfer contains about 7.4% more data than 100 GB, so it takes about 7.4% longer at the same speed.

File Transfer Calculator

Estimate real copy time across USB, Thunderbolt, internal drives, DAS, NAS, Ethernet, Wi-Fi and fiber by finding the slowest part of the complete path.

Transfer Scenario

Copy from a computer drive to storage attached by USB or Thunderbolt.

NAS / DAS Storage

Storage ConfigurationChoose Custom Array to model the enclosure and member drives instead of relying on a generic storage preset.

Data Set

Total Data

Data Unit

File LayoutBest case for sustained sequential read, write and network throughput.

Source Storage

Storage Type

Sustained Read SpeedMB/s

Sustained Write SpeedMB/s

Representative high-end PCIe 4.0 drive performance. Both values remain editable.

Destination Storage

Storage Type

Sustained Read SpeedMB/s

Sustained Write SpeedMB/s

Typical sustained speed for a healthy 2.5-inch portable hard drive. Both values remain editable.

Connection

Narrowest ConnectionPreviously labeled USB 3.1 Gen 2 or USB 3.2 Gen 2.

Connection Rate

Rate Unit

USB-C Does Not Set The Speed. It describes the connector. The host port, cable, dock or hub, enclosure and storage device negotiate to the slowest supported USB or Thunderbolt mode. Rates in Mbps or Gbps are bits per second; 1 Gbps equals 125 MB/s before overhead.

Copy Environment

Operating System

Copy MethodExplorer, Finder, cp or a similar local copy with large files.

Windows does not change the cable or drive ceiling. Defender scanning, NTFS or exFAT, SMB signing or encryption, drivers and the copy app can matter. Robocopy /J can help very large files, while /MT can help many small files. The calculator applies no hidden operating-system multiplier.

Advanced Assumptions

Link Efficiency%Physical signaling, framing and controller allowance, from 0 to 100%.

Copy Method Efficiency%Protocol, copy application and file-service allowance, from 0 to 100%.

File Layout Efficiency%Metadata and random-I/O allowance for this file mix, from 0 to 100%.

CPU / Security LimitOptionalMB/sOptional cap for encryption, checksums, antivirus, VPN or CPU limits.

Shared Controller LimitOptionalMB/sOptional measured or documented aggregate cap when both devices share a controller, dock or hub. No automatic 50% penalty is assumed.

Verify Data After CopyAdds a full read-back comparison using source read, destination read and connection limits.

Compare Common Connections

Uses the current data size, source, destination and file layout. Network rows use a healthy SMB planning factor; internet rows use a cloud-transfer factor.

Connection	Usable Path	Estimated Time	Limiting Stage
USB 2.0 (480 Mbps)	45 MB/s	1 Hr 35 Min 27 Sec	Connection
USB 5Gbps (USB 3.0 / Gen 1)	450 MB/s	35 Min 48 Sec	Destination Write
USB 10Gbps (USB 3.x Gen 2)	1 GB/s	35 Min 48 Sec	Destination Write
USB 20Gbps (USB 3.2 Gen 2x2)	2 GB/s	35 Min 48 Sec	Destination Write
USB 40Gbps (USB4)	3.9 GB/s	35 Min 48 Sec	Destination Write
Thunderbolt 4	3.36 GB/s	35 Min 48 Sec	Destination Write
Thunderbolt 5	6.72 GB/s	35 Min 48 Sec	Destination Write
Gigabit Ethernet	118.8 MB/s	37 Min 44 Sec	Connection
2.5 Gigabit Ethernet	296.9 MB/s	37 Min 20 Sec	Destination Write
10 Gigabit Ethernet	1.19 GB/s	37 Min 20 Sec	Destination Write
Wi-Fi Link (1,201 Mbps)	75.1 MB/s	59 Min 41 Sec	Connection
Fiber / Internet (1 Gbps)	112.5 MB/s	46 Min 18 Sec	Connection

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What Is the File Transfer Calculator?

The File Transfer Calculator estimates how long a real storage copy should take by modeling the complete path instead of treating the cable's advertised speed as the answer. Set the total data size and file layout, choose editable source and destination storage presets with separate sustained read and write speeds, then select the narrowest connection from legacy USB and current USB 5/10/20/40/80Gbps modes, Thunderbolt 1 through 5, SATA, PCIe, Ethernet from 100 Mbps through 800 Gbps, representative Wi-Fi links, measured fiber internet tiers or a custom rate. The calculation compares source read speed, usable connection throughput, destination write speed and optional CPU, security or shared-controller caps, then names the active bottleneck. DAS and NAS array presets are editable because enclosures, RAID levels, caching and disk models vary. Advanced controls cover link, protocol and small-file efficiency, a user-entered shared dock or controller limit, and an optional read-back verification pass. A comparison table shows how the same transfer would perform across common connections without pretending every device reaches its headline rate.

How It Works

Choose a transfer scenario, enter the total data size, and pick the closest source and destination storage types. For a NAS or DAS, switch Storage Configuration to Custom NAS/DAS Array, select whether it is the source or destination, then enter the enclosure's bay count, installed drives, RAID layout, member-drive type and efficiency. Select the slowest negotiated connection anywhere in the path, choose the copy method and file layout, then read the estimated completion time, usable throughput and bottleneck. Use Advanced Assumptions for measured shared-controller, CPU and security limits.

When to Use It

Use it before copying camera cards, moving a media library to an external drive, migrating between SSDs, choosing a USB or Thunderbolt enclosure, estimating a NAS backup window, testing whether 2.5 or 10 Gigabit Ethernet is worthwhile, planning a DAS or RAID transfer, or estimating a cloud upload from measured fiber speed.

Frequently Asked Questions

Does USB-C tell me the transfer speed?: No. USB-C describes the connector shape, not its data capability. A USB-C port or cable may carry USB 2.0, USB 5/10/20/40/80Gbps, Thunderbolt or another mode. The host, cable, dock or hub, enclosure and device negotiate to the slowest supported capability, so select the actual advertised or measured protocol.
Why does Thunderbolt 5 use 80 Gbps instead of 120 Gbps?: Thunderbolt 5 provides an 80 Gbps bidirectional base link and a 120/40 Gbps Bandwidth Boost mode intended for display-heavy traffic. Storage planning should use the 80 Gbps mode and the 64 Gbps PCIe data path rather than treating 120 Gbps as normal file-copy bandwidth.
Do Windows, macOS and Linux transfer at different speeds?: There is no defensible universal multiplier for an operating system. File system, drivers, copy software, antivirus or indexing, SMB or NFS settings, signing and encryption, CPU load, caching and file count matter more. The operating-system selector changes guidance only; it does not secretly alter the calculation.
How does the calculator handle NAS and DAS storage?: NAS and DAS describe how storage is attached, not a fixed speed. Enter the array's sustained read and write performance, then model the USB, Thunderbolt, Ethernet, Wi-Fi or fiber path separately. A NAS can be limited by its disks, RAID work, client and server NICs, switch uplink, protocol, CPU or destination drive.
Why can many small files take much longer?: Each file adds directory, permission, metadata and open/close work. Antivirus, checksums, network latency and hard-drive seeks can amplify that cost. The File Layout setting applies a visible planning efficiency, and archiving a folder before transferring it can sometimes improve throughput substantially.
What is the difference between GB and GiB?: GB is decimal: 1,000,000,000 bytes. GiB is binary: 1,073,741,824 bytes. A 100 GiB transfer contains about 7.4% more data than 100 GB, so it takes about 7.4% longer at the same speed.

Found an issue? Send Feedback. See our data sources and update policy for tools that depend on changing information.