Backup transfer time calculator
Estimate how long a backup, restore, replication or migration takes over a real-world connection.
What the calculator uses
Enter the amount of data, the nominal link speed in megabits per second, the expected link efficiency and an optional storage limit in megabytes per second. RetentionLab calculates the effective throughput, identifies the limiting factor and estimates the transfer duration.
The transfer-time formula
Available network throughput in decimal MB/s equals link speed in Mbps multiplied by efficiency, then divided by eight. If you supply a storage limit, the calculator uses whichever value is lower: available network throughput or storage throughput.
Transfer duration = data size ÷ effective throughput.
Example: transferring 1 TB over 100 Mbps
| Input | Value |
|---|---|
| Data size | 1 TB |
| Link speed | 100 Mbps |
| Link efficiency | 80% |
| Effective network throughput | 10 MB/s |
| Estimated duration | 27.78 hours |
If either the source or destination storage is limited to 5 MB/s, storage becomes the bottleneck and the estimate doubles to approximately 55.56 hours.
TB and TiB are different
The calculator supports decimal GB and TB as well as binary GiB and TiB. One TB is 1,000,000,000,000 bytes. One TiB is 1,099,511,627,776 bytes, so one TiB takes about 10% longer to transfer than one TB at the same throughput.
Choosing a realistic efficiency
A network rarely delivers its nominal rate entirely to one data transfer. Protocol overhead, latency, encryption, retransmissions, congestion and competing traffic reduce usable throughput. Use measurements from a representative transfer when possible. In an early planning estimate, compare more than one efficiency value to see the practical range.
Transfer time is only part of recovery time
A restore can also require archive retrieval, backup discovery, catalog loading, decryption, decompression, database recovery, application startup and validation. Some stages can overlap and others happen in sequence. Add them to the transfer estimate before comparing the result with a recovery time objective.
Does RetentionLab upload transfer information?
No. The values are calculated in your browser and are not sent to a calculation server or saved by the application.
For byte conversions, formulas, assumptions and worked examples, read the transfer methodology.