USB and Thunderbolt Transfer Speed Calculator

USB and Thunderbolt Transfer Speeds

Local transfers between drives, cameras, and peripherals use USB or Thunderbolt interfaces. While theoretical speeds are high, real-world performance varies significantly.

Interface Specifications

Interface	Theoretical Max	Real-World Max	Typical
USB 2.0	480 Mbps	280 Mbps	200 Mbps
USB 3.0 (3.2 Gen 1)	5 Gbps	3.2 Gbps	2.4 Gbps
USB 3.1 (3.2 Gen 2)	10 Gbps	7.5 Gbps	5.0 Gbps
USB 3.2 Gen 2x2	20 Gbps	15 Gbps	10 Gbps
USB4	40 Gbps	32 Gbps	20 Gbps
Thunderbolt 3	40 Gbps	22 Gbps	18 Gbps
Thunderbolt 4	40 Gbps	32 Gbps	24 Gbps
Thunderbolt 5	80 Gbps	60 Gbps	40 Gbps

Transfer Time: 1 TB External Drive Backup

USB 2.0 (200 Mbps):    1 TB * 8 / 0.2 Gbps = 40,000 sec = 11h 6m
USB 3.0 (2.4 Gbps):    1 TB * 8 / 2.4 Gbps = 3,333 sec = 55m 33s
USB 3.1 (5.0 Gbps):    1 TB * 8 / 5.0 Gbps = 1,600 sec = 26m 40s
Thunderbolt 3 (18 Gbps): 1 TB * 8 / 18 Gbps = 444 sec = 7m 24s
Thunderbolt 5 (40 Gbps): 1 TB * 8 / 40 Gbps = 200 sec = 3m 20s

Bottleneck: Drive Speed vs Interface Speed

The USB/Thunderbolt interface is often not the bottleneck. The drive itself may limit throughput:

Drive Type	Sequential Read	Sequential Write
HDD 5400 RPM	100-120 MB/s	80-100 MB/s
HDD 7200 RPM	150-200 MB/s	130-180 MB/s
SATA SSD	500-550 MB/s	450-520 MB/s
NVMe SSD	3,500-7,000 MB/s	2,000-6,500 MB/s

A USB 3.0 connection (400 MB/s real) is faster than any HDD and most SATA SSDs. Only NVMe drives benefit from USB 3.2 Gen 2 or Thunderbolt.

Small Files Penalty

Transfer speeds drop dramatically with many small files due to filesystem overhead:

10,000 photos (5 MB each = 50 GB total):
Sequential: 50 GB in 2 minutes at USB 3.0 speeds
Actual: Often 10-30 minutes due to per-file overhead