Download time calculator
Enter the file size and your connection speed. You get the time it takes and a table of the same download at other speeds.
Free · no signup Runs in your browser
How long will my download take?
Multiply the file size in bytes by 8 to get bits, and divide by your speed in bits per second. A 2 GB (2,000,000,000 bytes) file at 100 Mbps is 16,000,000,000 ÷ 100,000,000 = 160 seconds, about 2 minutes 40 seconds. Speeds are sold in megabits (Mbps) but file sizes are in megabytes, and a byte is 8 bits, so divide Mbps by 8 for MB/s: 100 Mbps is at most 12.5 MB/s. Real downloads are usually a bit slower, so allow some overhead.
Why we built this tool
Is a 50 GB game going to be ready tonight? Will a 4 GB backup finish before the office closes? How long to upload a video to a client? Answers come from a simple division, but the units trip everyone up: megabits against megabytes, decimal gigabytes against binary gibibytes, and a speed test that says 300 when the download bar shows 37. This calculator takes the units you have, allows for overhead, and gives the time, the effective speed in both units and the same download at other common speeds.
Everything is worked out in your browser. Nothing you enter is sent anywhere.
How it works
Time is the amount of data divided by the rate. The size is turned into bytes using the unit you choose: decimal units (KB, MB, GB, TB) are powers of 1,000, which is what most storage and download pages use, while binary units (KiB, MiB, GiB, TiB) are powers of 1,024, which many operating systems use when they say MB or GB. The speed is turned into bits per second: 1 Mbps is 1,000,000 bits per second, and 1 MB/s is 8,000,000. The overhead box lowers the usable speed by a percentage to allow for protocol headers, retransmissions, Wi-Fi interference and server limits; 5 to 15% is typical for a good wired connection. Then time = bytes × 8 ÷ effective bits per second, shown in days, hours, minutes and seconds.
How to use it
- Enter the file size and choose its unit (MB and GB are decimal; MiB and GiB are binary).
- Enter your speed from a speed test or your plan, and choose Mbps, Gbps or MB/s.
- Add an overhead percentage if you want a realistic figure (try 10).
- Read the time, then check the table to see what a faster plan would do.
- For uploads, use your upload speed, which is often much lower than download.
Megabits and megabytes
The quick conversions.
| Plan speed | Best-case MB/s | Time for 1 GB | Time for 50 GB |
|---|---|---|---|
| 25 Mbps | 3.1 | 5 min 20 s | 4 h 27 min |
| 100 Mbps | 12.5 | 1 min 20 s | 1 h 7 min |
| 500 Mbps | 62.5 | 16 s | 13 min 20 s |
| 1 Gbps | 125 | 8 s | 6 min 40 s |
| 10 Gbps | 1,250 | 0.8 s | 40 s |
Use cases
- Planning a large game, software or operating system download
- Estimating a backup or a cloud upload before you start it
- Deciding whether to upgrade your internet plan
- Sending a large video or photo set to a client
- Working out transfer time for a server migration
- Explaining to someone why their 'fast' connection still takes a while
Problems you may run into
Most surprises come from units and real-world limits.
| What you see | Likely cause | What to do |
|---|---|---|
| The download is much slower than the table says | The server, Wi-Fi or other devices are the limit, not your plan | Test with a cable, pause other downloads and try again; add overhead |
| My file is 'GB' but the numbers differ from my computer | Decimal GB (1,000,000,000 bytes) against binary GiB (1,073,741,824) | Choose the unit your system reports, or use bytes |
| The speed test says 300 but the download shows 37 | 300 Mbps is 37.5 MB/s | Divide Mbps by 8 for MB/s |
| Uploads take far longer | Many plans have a lower upload speed | Enter your upload speed from a speed test |
| The time looks unrealistically short | The speed is the plan maximum | Use a measured speed and an overhead of 10 to 20% |
| Mobile data caps | A fast connection does not remove a data cap | Check how much data the download uses, not just the time |
Why real speeds are lower
Your plan speed is a ceiling. Each packet carries headers, some packets are resent, encryption adds a little, Wi-Fi shares the air with neighbours, and the server you download from may serve many people at once. Wired connections usually reach 90% or more of the plan on a good day; Wi-Fi and busy servers can be far lower. For a safe estimate, measure your speed with a test close to the time you will download.
The formula
How the answer is worked out.
bytes = size × unit; decimal: KB = 1,000, MB = 1,000,000, GB = 10⁹, TB = 10¹²; binary: KiB = 1,024, MiB = 1,048,576, GiB = 2³⁰, TiB = 2⁴⁰bits per second = speed × unit × (1 − overhead); 1 Mbps = 1,000,000 bits per second; 1 MB/s = 8,000,000time in seconds = bytes × 8 ÷ bits per secondMB/s = Mbps ÷ 8
Results are the time if the connection holds the entered speed for the whole transfer. Overhead is a single percentage you choose. Results over a day are shown in days and hours.
Example: a 50 GB game on a 300 Mbps plan
Decimal 50 GB at 300 Mbps with 10% overhead.
- Bytes50 × 1,000,000,000 = 50,000,000,000; bits = 400,000,000,000
- Effective speed300 Mbps × 0.9 = 270 Mbps
- Time400,000,000,000 ÷ 270,000,000 = 1,481 seconds
About 24 minutes 41 seconds
With no overhead it is 22 minutes 13 seconds.
Terms on this page
- Mbps
- Megabits per second: how internet speed is usually sold.
- MB/s
- Megabytes per second: how download progress is usually shown; Mbps ÷ 8.
- Overhead
- The part of the line speed used by headers, resends and sharing.
Common questions
How do I convert Mbps to MB/s?
Divide by 8. 100 Mbps is 12.5 MB/s.
What is the difference between MB and MiB?
MB is 1,000,000 bytes and MiB is 1,048,576 bytes.
Why is my download slower than my plan?
Overhead, Wi-Fi, other devices and the server all take a share.
How long does 1 GB take on 100 Mbps?
About 80 seconds at best.
Does it work for uploads?
Yes, use your upload speed.
Is anything I enter sent to a server?
No. The calculation happens in your browser and nothing you type leaves your device.
Where these numbers come from
- Wikipedia — Data-rate units Bits and bytes per second, and the prefixes.
- Wikipedia — Binary prefix Decimal (KB, MB) and binary (KiB, MiB) prefixes.
Last verified 2026-10-25 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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