Practical AtlasIndependent referenceFree online tool
File transfer time calculator
Estimate how long a copy really takes from observed sustained throughput, rather than from the speed printed on the enclosure.
Estimate a measured copy.
Use observed MB/s rather than an interface logo to expose the real bottleneck.
COMMON WAYS TO ASK
- How long to copy these files?
- Why is my external drive so slow?
- Estimate copy time
What this calculator tells you.
Estimate copy time from the real file size and the throughput you actually observe, rather than from the speed printed on the enclosure. Interface ratings are ceilings, not rates.
Moving 500 GB to an external drive
Questions people ask next.
Why is the copy slower than the port speed?
A port rating is the maximum the interface can carry. The drive, the files, the file system, and the other end all cap the real rate, and many small files are far slower than one large one.
How do I find my sustained throughput?
Start a large copy and read the rate after it settles, not in the first seconds. Early speed often reflects a cache that empties once the transfer continues.