Computing & Networks
Data Transfer Calculator
Calculate transfer time, required transfer speed, or the amount of data transferred using file size, bandwidth, and time.
Transfer information
Decimal units such as GB and Mbps use powers of 1000. Binary units such as GiB use powers of 1024.
Transfer time
Enter your transfer information and calculate the result.
How data transfer time is calculated
Transfer time depends on the amount of data being moved and the transfer speed. Because network speeds are commonly measured in bits per second while file sizes are commonly measured in bytes, the units must be converted before dividing.
Bits vs bytes
One byte contains eight bits. That means 100 Mbps is not the same as 100 MB/s. A theoretical 100 Mbps connection carries 12.5 MB per second before accounting for real-world overhead.
Decimal vs binary storage units
KB, MB, GB, and TB use powers of 1000. KiB, MiB, GiB, and TiB use powers of 1024. This calculator supports both systems so the units can match the value you are working with.
Data Transfer Calculator Guide
This data transfer calculator can calculate transfer time, required transfer speed, or the amount of data transferred. It supports common decimal storage units such as GB and TB, binary storage units such as GiB and TiB, and transfer speeds measured in both bits per second and bytes per second.
How to Calculate Data Transfer Time
To calculate how long a file transfer will take, divide the amount of data by the transfer rate after converting both values into compatible units.
The main complication is that file sizes are usually measured in bytes while network speeds are usually measured in bits per second.
Because one byte contains eight bits, the calculator converts the values automatically before calculating transfer time.
Example: 100 GB at 100 Mbps
A 100 GB transfer over a sustained 100 Mbps connection takes approximately 8,000 seconds.
Transfer speed: 100 Mbps
Transfer time: 2 hours, 13 minutes, 20 seconds
This is a mathematical estimate based on a constant 100 Mbps transfer rate. Real-world transfers are often slower because of protocol overhead, congestion, storage performance, wireless conditions, server limits, and other factors.
Mbps vs MB/s
Mbps means megabits per second, while MB/s means megabytes per second. They are not the same unit.
Therefore, a theoretical 100 Mbps connection corresponds to 12.5 MB/s.
Likewise, 1 Gbps equals a theoretical 125 MB/s before accounting for overhead.
Common Transfer Speed Conversions
How to Calculate Required Transfer Speed
If you know how much data must be transferred and how quickly the transfer must finish, you can calculate the required transfer rate.
For example, transferring 100 GB in two hours requires approximately 111.11 Mbps of sustained throughput.
Time: 2 hours
Required speed: approximately 111.11 Mbps
In practice, a connection rated exactly at the calculated speed may not complete the transfer within the desired time because actual throughput is often lower than the advertised maximum.
How to Calculate Data Transferred
If you know the transfer speed and the amount of time the connection is active, you can estimate how much data can be moved.
A sustained 100 Mbps transfer for one hour moves approximately 45 GB of decimal data.
Time: 1 hour
Data transferred: approximately 45 GB
GB vs GiB
GB and GiB represent different quantities of data.
GB uses the decimal system, based on powers of 1000. GiB uses the binary system, based on powers of 1024.
This difference becomes increasingly noticeable with larger storage capacities.
Decimal Data Units
Binary Data Units
File Transfer Time Examples
Internet Download Time vs Local File Transfer Time
The same mathematics can be used for internet downloads and local network transfers, but the limiting factors may be different.
An internet download may be limited by your ISP connection, the remote server, congestion, Wi-Fi performance, or routing conditions.
A local transfer may instead be limited by Ethernet speed, Wi-Fi speed, USB speed, storage devices, NAS performance, CPU load, or network protocol overhead.
Why Is My Actual Transfer Slower?
Advertised network speeds are usually maximum link rates rather than a guarantee of usable application throughput.
Real-world transfer speed can be reduced by factors including:
- Ethernet, Wi-Fi, TCP/IP, SMB, or other protocol overhead
- Wireless interference and signal quality
- Network congestion
- Slow hard drives or solid-state drives
- Server-side bandwidth limits
- CPU or encryption overhead
- Other devices sharing the connection
- Packet loss or retransmissions
Transfer Speed vs Internet Plan Speed
Internet service is commonly advertised in Mbps or Gbps. File transfer applications often display speed in MB/s instead.
For example, a 1 Gbps internet connection has a theoretical maximum of 125 MB/s because eight bits make one byte.
Seeing less than 125 MB/s does not necessarily mean something is wrong. Protocol overhead and other bottlenecks reduce real throughput.
Data Transfer Calculator for NAS and Local Networks
The calculator can also estimate transfer times for network-attached storage, home servers, backups, workstation transfers, and other local networking tasks.
For example, you can estimate how long a 2 TB backup would theoretically take over a 1 Gbps Ethernet connection, or determine the sustained network speed required to complete a backup within a particular time window.
Data Transfer Calculator Limitations
The results assume a constant transfer rate for the entire duration. Actual throughput can vary throughout a transfer.
The calculator also reports mathematical throughput rather than attempting to estimate protocol overhead or the performance of specific hardware, storage devices, internet providers, or network configurations.
For planning purposes, real transfers should generally be expected to take longer than the theoretical minimum calculated from a connection's maximum rated speed.