Download Time Calculator

Work out how long a download or file transfer takes from the file size and your connection speed. Handles all the common size and speed units, breaks the duration down readably, compares typical connections and can also solve for speed or file size.

Runs entirely in your browser. Nothing you put in here gets uploaded.

File size

Connection speed

100 Mbps is 12.5 MB/s. Divide bits by 8 to get bytes.

Real-world overhead

Headers, Wi-Fi loss and busy servers eat into the advertised speed. 5 to 15% is realistic.

700 MB at 100 Mbps takes

56 seconds

Seconds: 56 s
Minutes: 0.933 min
Hours: 0.0156 h
Speed: 100 Mbps

On a typical connection

Typical real-world speeds, so treat the times as ballpark.

Connection	Speed	Time
56k modem dial-up	0.056 Mbps	1 day 3 hours 46 minutes
3G HSPA, good signal	8 Mbps	11 minutes 40 seconds
DSL 16 Mbit line	16 Mbps	5 minutes 50 seconds
4G LTE, typical	30 Mbps	3 minutes 7 seconds
100 Mbit fiber or a cable plan	100 Mbps	56 seconds
5G typical	200 Mbps	28 seconds
Gigabit fiber 1,000 Mbit line	1,000 Mbps	5.6 seconds

About the Download Time Calculator Tool

This tool works out how long a download or file transfer takes from the file size and your connection speed. It handles the part everyone trips over: internet plans are sold in megabits per second, files and download managers count in megabytes, and one byte is 8 bits.

You can also turn the question around. Give it a size and a time to get the speed you need, or a speed and a time to see how much data fits through. An overhead percentage makes the estimate realistic, and a table shows the same file on common connections from dial-up to gigabit fiber.

What you can do

Calculate how long a download takes from the file size and your connection speed.
Convert a speed between Mbps and MB/s and see both readings at once.
Find the connection speed you need to move a file in a given time.
See how much data you can transfer in an hour on your connection.
Compare download times on 3G, 4G, 5G, DSL, 100 Mbit fiber and gigabit.
Add an overhead percentage for a realistic estimate instead of the theoretical best case.

How to use the Download Time Calculator

1Pick what to solve for: the download time, the needed speed or the possible size.
2Enter the two values you know, each with its unit.
3Add an overhead percentage if you want a real-world estimate.
4Read the result, copy it in the unit you need, or compare connections in the table below.

Megabits, megabytes and the factor of 8

Internet plans are advertised in megabits per second (Mbps) but file sizes are measured in megabytes (MB), and one megabyte is 8 megabits. That is why a 100 Mbps line tops out around 12.5 MB per second, not 100. The calculator keeps the two apart: pick a bit-based unit like Mbps for a plan or a byte-based unit like MB/s from a download manager, and the field shows the other reading right underneath.

KB or KiB

Size units come in two families. Decimal units step in thousands, so 1 GB is 1,000,000,000 bytes. Binary units step in powers of 1024, so 1 GiB is 1,073,741,824 bytes, about 7% more. Operating systems and download tools mix the two freely, which is why a 700 MB file can read as 667 MiB elsewhere. The size picker offers both families. For conversions between other measurement units there is the Unit Converter.

Why real downloads are slower

The advertised speed is a ceiling, not a promise. Protocol headers, Wi-Fi retransmissions, a busy server on the other end and other devices sharing your line all shave something off. The overhead field subtracts a percentage before calculating, and 5 to 15% is a realistic allowance on a healthy connection. The connection table applies the same overhead, so its times stay comparable with your result.

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