taap.digitalnetwork engineering toolkit

How long does it take to transfer 100 GB at 1 Gbps?

Answer
14 min 49 s with 10% overhead

100 GB is 800 Gbit. At 1 Gbps minus 10% overhead (900 Mbps effective) that takes 14 min 49 s. The theoretical line-rate minimum is 13 min 20 s.

xfer-time · adjust the values
%

The calculation

100 GB × 8 = 800 Gbit
800 Gbit ÷ (1 Gbps × 0.9) = 14 min 49 s

Sizes and rates use decimal units (1 GB = 109 bytes, 1 Gbps = 109 bit/s). If your source reports TiB or GiB, the data is about 10% or 7% larger respectively.

Effect of overhead

OverheadTransfer time
0%13 min 20 s
5%14 min 2 s
10%14 min 49 s
20%16 min 40 s
30%19 min 3 s

When it takes longer

A single TCP flow over a long-RTT path is capped at window ÷ RTT, so check the bandwidth-delay product before blaming the link. Disk throughput, encryption on one CPU core (scp, SMB signing) and shared links are the other usual suspects. Parallel streams (rclone --transfers 8, iperf3 -P 4) usually close the gap.

More questions like this

1 TB @ 1 Gbps1 TB @ 10 Gbps10 TB @ 10 Gbps50 GB @ 100 Mbps500 GB @ 1 Gbps4 TB @ 2.5 Gbps1 TB @ 100 Mbps

Frequently asked questions

What is 1 Gbps in MB/s?

125 MB/s at line rate, about 112.5 MB/s with 10% overhead.

Why use 10% overhead?

Ethernet, IP and TCP headers take about 5% at a 1500-byte MTU; the rest covers retransmissions, protocol chatter and imperfect pipelining. It is a realistic default for a healthy path.