Internet & Network Tools

Download Time Calculator

Download Time Calculator is part of Toolspire and is ready as soon as this page loads. One decimal gigabyte at 100 Mbps is 1 minute 20 seconds, because a byte is eight bits. The speed test measures a line. This page only divides a size by a rate you type.

Runs in this tabFreeNo account

File sizeUnitLink speed (Mbps)

Transfer time

1 min 20 sec

100 Mbps moves 12.5 decimal MB/s. Unrounded time 80 seconds.

1 GB here is 1,000,000,000 bytes, and 1 Mbps is 1,000,000 bits a second. A real transfer is slower once headers and the path get involved.

On this page

What you can do here

Megabits in, minutes out

The speed box is Mbps, the unit an ISP prints. The size box is MB, GB or TB of decimal bytes.

The 8× is visible

The detail shows MB/s as Mbps divided by 8, so a 100 Mbps line is not treated as 100 megabytes a second.

A clock, not a raw second count

Eighty seconds is shown as 1 min 20 sec. The unrounded seconds stay in the detail.

The sequence

How to use the Download Time Calculator

1
Type the file size in decimal units
A shop that says 1 GB almost always means 1,000,000,000 bytes. Use GB for that. A 1024-based gibibyte is about 7% larger and is not what this page divides.
2
Type the link speed in Mbps
Use the rate you expect to get, not the number on the router box, if you already know the line is slower than the plan.
3
Read the clock as a floor
The result is the time if every bit of the plan is payload. Add time for a weak signal or a capped server.

Worth knowing

Download Time Calculator on Toolspire: time is size in bytes × 8 ÷ bits per second. A byte is eight bits, which is the factor people forget.
1 GB at 100 Mbps is 1 min 20 sec. 1 GB here is 1,000,000,000 bytes, and 100 Mbps is 100,000,000 bits a second.
1 Mbps is 0.125 MB/s of decimal bytes. The detail prints that MB/s figure next to the clock time.
The page does not measure the connection. Packet headers, Wi-Fi and a busy server all make a real transfer slower than this division.

Why 100 Mbps is not 100 MB/s

Network speeds are sold in megabits. Files are sized in megabytes. There are eight bits in a byte, so a 100 Mbps plan moves 12.5 decimal megabytes a second when every bit is file data. Dividing a gigabyte by 100, as if the units matched, gives 10 seconds and is wrong by a factor of eight. This page keeps the units apart: you pick MB, GB or TB, you type Mbps, and the 8× happens in the formula. It does not open a socket and it does not time your own line. The speed test is the page that does that.

FAQ

Questions about Download Time Calculator

Where does Download Time Calculator run?

Download Time Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

How long is a 1 GB download at 100 Mbps?

1 minute 20 seconds, using a decimal gigabyte and a decimal megabit. 1,000,000,000 bytes × 8 ÷ 100,000,000 bits per second = 80 seconds.

Is a GB here 1024 megabytes?

No. MB, GB and TB on this page are powers of 1,000. A gibibyte (1024³) would take about 7% longer at the same megabit rate.

Why is my real download slower?

The formula assumes the link is full of file bytes. TCP headers, Wi-Fi retries, a busy disk and a server that will not send that fast all add time.

Does this test my connection?

No. You type the speed. The internet speed test is the tool that measures download, upload, ping and jitter.

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Last updated 23 October 2026Report a problem or suggest a feature