taap.digitalnetwork engineering toolkit

How long does it take to transfer 500 GB at 1 Gbps?

Answer
1 h 14 min 4 s with 10% overhead

500 GB is 4,000 Gbit. At 1 Gbps minus 10% overhead (900 Mbps effective) that takes 1 h 14 min 4 s. The theoretical line-rate minimum is 1 h 6 min 40 s.

xfer-time · adjust the values
%

The calculation

500 GB × 8 = 4,000 Gbit
4,000 Gbit ÷ (1 Gbps × 0.9) = 1 h 14 min 4 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%1 h 6 min 40 s
5%1 h 10 min 11 s
10%1 h 14 min 4 s
20%1 h 23 min 20 s
30%1 h 35 min 14 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

100 GB @ 1 Gbps1 TB @ 1 Gbps1 TB @ 10 Gbps10 TB @ 10 Gbps50 GB @ 100 Mbps4 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.