Bandwidth & Transfer Time Calculator

How long will a 200 GB server backup take to upload? Will your 1 Gbps fiber still feel like gigabit once a VPN is on? Is your host's 1 TB monthly allowance enough for 100,000 page views? This bandwidth and transfer time calculator answers all three with plain arithmetic, so you can plan migrations, backups, streaming and hosting plans before you commit to them.

How to use it

1. Choose a mode: Transfer time, Site traffic or Streaming.
2. In Transfer time, enter the data size and your connection speed, then set the protocol or VPN overhead. Quick presets cover no overhead, WireGuard, OpenVPN over UDP and OpenVPN over TCP.
3. In Site traffic, enter your average page weight and monthly page views to estimate monthly transfer and the average bandwidth your server must sustain.
4. In Streaming, enter a bitrate and the hours watched to see how much data a match, film or series uses.

Understanding the output

Bits vs. bytes

Internet speeds are sold in megabits per second (Mbps) while files are measured in megabytes (MB). There are 8 bits in a byte, so a 100 Mbps connection moves at most 12.5 MB per second. The calculator uses decimal units the way ISPs and hosting companies do: 1 GB is 1,000 MB.

Effective speed and overhead

Every protocol adds headers, and VPNs add encryption and encapsulation on top. The overhead slider reduces the raw line speed to an effective speed, then shows the resulting transfer time next to the no-overhead best case and the time lost to overhead. The presets are rough typical figures: WireGuard tends to be lean, while OpenVPN over TCP usually costs the most. Your real numbers depend on CPU, MTU settings and the server, so treat them as a starting point and measure your own link.

Monthly traffic and average bandwidth

Site traffic mode multiplies page weight by page views to get monthly transfer, then spreads it across a 30-day month to show the average sustained bandwidth. Real traffic is spiky, which is why a 5× spike figure is shown as well.

Pro tips

• Measure, then plug in. Run a speed test with and without your VPN and use the difference as your overhead percentage.
• Plan backups around upload speed. Home and office connections often upload far slower than they download; enter the upload figure for offsite backups.
• Budget for the first full backup. Incremental backups are small, but the initial seed can take days on a slow uplink.
• Remember the CDN. If a CDN serves your images and scripts, your origin server transfers only a fraction of the site-traffic estimate.

Common mistakes and use cases

The most common mistake is mixing up MB and Mb, which makes every estimate eight times too optimistic or pessimistic. The second is assuming the advertised speed is what a single transfer gets; Wi-Fi, disk speed, server limits and TCP behavior all take a share, so treat the result as a best case.

Typical uses:

• VPN performance: understanding VPN encryption overhead on gigabit fiber and WireGuard vs. OpenVPN on low-power routers.
• Backups: sizing the upload window for automated offsite backups with Duplicati.
• Hosting plans: checking whether "unlimited" really is, in the hidden costs of unlimited shared hosting.
• Streaming: estimating data use for Smart DNS vs. full VPN tunnels for sports streaming.

Further reading

The web.dev guide to fast load times explains how page weight affects real users, and the Bufferbloat project covers why a fast line can still feel laggy. To work out the network ranges those transfers travel over, use the subnet and CIDR calculator.