Calculate transfer time, bandwidth or data size
A data transfer calculator connects three quantities: how much data needs to move, how fast it can move, and how long the connection is available. Use Transfer time for a download or backup estimate. Choose Required bandwidth when you have a deadline, or Data transferred when a connection speed and time window are already known.
Start with the two values you know, select their units, and set an efficiency assumption. Results update immediately. The presets load complete examples, including the efficiency setting; Reset restores the 10 GB, 100 Mbps, 100% example. Changing a unit reinterprets the number in that field, so check both before copying a result.
Effective rate = nominal rate × efficiency
Time in seconds = size in bytes × 8 ÷ effective bits/s
Required nominal bits/s = size in bytes × 8 ÷ seconds ÷ efficiency
Mbps vs MB/s, and GB vs GiB
The case of a single letter changes the result by a factor of eight. A network connection rated at 100 Mbps has a theoretical byte rate of 12.5 MB/s. If a transfer application already reports 12.5 MB/s, choose MB/s directly; do not multiply it by eight yourself.
| Unit | Meaning in this calculator |
|---|---|
| 1 byte (B) | 8 bits |
| 1 MB | 1,000,000 bytes |
| 1 MiB | 1,048,576 bytes |
| 1 GB | 1,000,000,000 bytes |
| 1 GiB | 1,073,741,824 bytes |
| 1 Mbps | 1,000,000 bits per second |
Decimal storage units use powers of 1,000; binary units with an “i” use powers of 1,024. Select the unit actually reported by your source. See NIST’s definitions of binary prefixes for the distinction. The calculator keeps that choice explicit rather than silently treating GB as GiB.
Three practical transfer estimates
Download a 10 GB archive
≈ 13 min 20 s100 Mbps at 100% efficiency: the theoretical transfer time, before any slowdown.
Try the example presets ↑Move a 100 GB backup
≈ 14 min 49 s1 Gbps at an assumed 90% efficiency. This is a planning assumption, not a measured network result.
Try the example presets ↑Meet a one-hour migration window
≈ 246.914 MbpsFind the nominal link speed needed for 100 GB in one hour, assuming 90% efficiency.
Try the example presets ↑These are calculated scenarios, not measured transfers or advertised service guarantees. The one-hour example is a nominal bandwidth requirement: choose capacity with room for other traffic and changes in throughput.
How long does a 10 GB file take to transfer?
This comparison uses decimal GB and Mbps, a constant connection speed, and no setup delay. The 90% column applies an illustrative efficiency assumption to the same nominal link speed.
| Link speed | At 100% efficiency | At 90% efficiency |
|---|---|---|
| 10 Mbps | ≈ 2 h 13 min 20 s | ≈ 2 h 28 min 9 s |
| 50 Mbps | ≈ 26 min 40 s | ≈ 29 min 38 s |
| 100 Mbps | ≈ 13 min 20 s | ≈ 14 min 49 s |
| 500 Mbps | ≈ 2 min 40 s | ≈ 2 min 58 s |
| 1 Gbps | ≈ 1 min 20 s | ≈ 1 min 29 s |
Plan for the slowest part of the transfer
For an upload, start with the sender’s available upload bandwidth. For a download, the source server may be slower than your access connection. A fast network also cannot move data faster than the disks and applications at its ends can read and write it.
Efficiency is a planning input, not a precise protocol-overhead simulation. Small files, round trips, retries, competing traffic, encryption and storage stalls can all change useful throughput. Test a representative sample when the deadline matters, then use the observed rate at 100% efficiency or apply an explicit additional margin.
A migration window may also include packaging, checksums, verification and a final incremental sync. This calculator estimates the transfer portion only. ESnet’s transfer-planning guidance explains why nominal network capacity alone is not enough to predict application throughput.
Data transfer calculator FAQ
How do I calculate data transfer time?
Convert the data size to bits, then divide by effective bits per second. For decimal GB and Mbps, seconds = GB × 8,000 ÷ (Mbps × efficiency). Use efficiency as a fraction: 90% is 0.9. The estimate assumes a steady rate for the entire transfer.
How long does it take to transfer 1 GB at 100 Mbps?
At 100% efficiency, 1 decimal GB takes 80 seconds, or 1 minute 20 seconds. At an assumed 90% efficiency, it takes about 88.9 seconds. A 1 GiB file is larger than 1 GB and takes about 85.9 seconds at the same ideal 100 Mbps rate.
What is the difference between Mbps and MB/s?
Mbps measures megabits per second; MB/s measures megabytes per second. One byte is eight bits, so 100 Mbps equals 12.5 MB/s before any reduction for overhead or other bottlenecks. This calculator uses decimal prefixes for Mbps and MB/s.
Which efficiency percentage should I choose?
100% shows the ideal constant-rate limit. A lower percentage represents your own assumption about the share of nominal speed available for useful data; there is no single percentage that fits every transfer. If you enter measured file-transfer throughput, use 100% unless you deliberately want an additional margin.
Can I use this as an upload time calculator?
Yes. Enter the upload speed available to the sender, rather than its advertised download speed. The receiving connection, storage and application may impose lower limits. Use the rate available to this transfer, not the combined capacity of unrelated links.
Does the calculator measure my internet speed?
No. It calculates from the numbers you enter. It does not send a test file, probe a server or measure latency. Actual transfers may vary with congestion, protocol behavior, disk performance, CPU load and pauses.
Can it estimate monthly data transfer?
Choose Data transferred, enter a sustained rate, then enter the number of days. A day is exactly 24 hours here; enter the number of days in your billing period. This models continuous use and does not calculate provider charges or decide which traffic a provider bills.
Are my files or inputs uploaded?
No file is needed. The calculation runs in your browser without a calculation API. This tool does not persist input values or add them to the URL. The copy button exports a text summary of the result and its assumptions.