50 GB at 100 Mbit/s with 5 % overhead
- File size
- 50 GB
- Connection speed
- 100 Mbit/s
- Protocol overhead
- 5%
- Time in seconds
- 4,210.53 s
- Effective speed
- 95 Mbit/s
Checked against: 50 × 8 × 10⁹ bits ÷ (100 × 10⁶ × 0.95) bit/s = 4210.526… s
Download time calculator
Calculate how long a file takes to download or upload from its size in MB, GB or TB and your internet speed in Mbps, allowing for protocol overhead.
By AdminDrafted with AI writing toolsUpdated Checked examples: 5
Download time
1 h 10 min 10 s
Download time: 1 h 10 min 10 s
- Time in seconds
- 4,210.53s
- Effective speed
- 95Mbit/s / 11.875MB/s
Real downloads also depend on the server, Wi-Fi signal and other traffic, so actual times are often longer.
At 100 Mbit/s with 5% overhead, the useful rate is 11.88 MB/s, so 50 GB takes 1 h 10 min 10 s.
Same file at common connection speeds
How it's calculated S
Size in bits
1 byte = 8 bits. GB means 10⁹ bytes; GiB means 2³⁰ bytes.
Speed after overhead
Time
That is 1 h 10 min 10 s.
About the download time calculator
Download time is file size divided by the useful data rate. The calculator turns the size into bits (1 byte = 8 bits; GB means 10⁹ bytes and GiB means 2³⁰ bytes), takes the connection speed in bits per second, and removes the share of each packet taken by protocol headers: time = bits ÷ (speed × (1 − overhead)).
People use it before downloading a game or a cloud backup, and to judge whether a faster plan is worth paying for. The default, a 50 GB file on a 100 Mbit/s line with 5% overhead, takes 1 h 10 min 10 s; at 1,000 Mbit/s the same file takes about 7 minutes.
The result is an estimate under the chosen assumptions. The 5% default is an illustrative rounded overhead assumption for TCP/IPv4 over Ethernet; the server’s own limit, Wi-Fi signal and other traffic are not modelled. For an upload, enter your upload speed, which on asymmetric lines such as ADSL is lower than the download speed.
In the formula, S is file size in bits, r is line speed in bits per second and h is the overhead fraction (5% means h = 0.05). The result t is in seconds.
How to calculate download time
Divide the file size in bits by the connection speed in bits per second. A 1 GB file is 8,000 megabits, so at 100 Mbps it takes 8,000 ÷ 100 = 80 seconds, or about 84 seconds with 5% protocol overhead. For an upload, use your upload speed.
The download time formula
t = S ÷ [r × (1 − h)], where S is the file size in bits, r the line speed in bits per second and h the overhead as a fraction (5% is 0.05). For a 50 GB game on a 100 Mbps line with 5% overhead:
- Size in bits: 50 × 10⁹ bytes × 8 = 400,000,000,000 bits.
- Useful rate: 100,000,000 × 0.95 = 95,000,000 bits per second.
- Time: 400,000,000,000 ÷ 95,000,000 ≈ 4,210.5 seconds, about 1 hour 10 minutes.
At 1,000 Mbps the same file takes about 7 minutes. Doubling the speed halves the time, and doubling the size doubles it.
Download time chart
Sizes are decimal GB except the GiB row, and every row assumes a steady rate for the whole transfer.
| File size | Connection speed | Overhead | Time in seconds |
|---|---|---|---|
| 1 GB | 100 Mbit/s | 0% | 80 |
| 1 GB | 100 Mbit/s | 5% | 84.210526 |
| 50 GB | 100 Mbit/s | 5% | 4210.526316 |
| 1 GiB | 1 Gbit/s | 0% | 8.589935 |
| 4.7 GB | 25 Mbit/s | 10% | 1671.111111 |
| 0 GB | 100 Mbit/s | 5% | 0 |
The 4.7 GB row, a single-layer DVD image, comes to 27 minutes 51 seconds.
Mbps vs MB/s
Internet plans are sold in megabits per second (Mbps or Mbit/s); browsers and download managers usually show megabytes per second (MB/s). A byte is 8 bits, so divide Mbps by 8: 100 Mbps is at most 12.5 MB/s, or 11.875 MB/s after 5% overhead.
Check the capital B before copying a rate. 100 MB/s is eight times faster than 100 Mbps.
GB vs GiB
Stores and internet providers count 1 GB as 1,000,000,000 bytes; a GiB is 1,073,741,824 bytes (NIST's binary-prefix reference). Windows File Explorer counts in GiB but labels them GB, so a 50 GB download shows there as about 46.6 GB.
A size copied from Windows is therefore in GiB, and it takes longer: at 100 Mbps with no overhead, 1 GiB takes 85.9 seconds against 80 seconds for 1 GB.
Why downloads run slower than your plan
Part of every packet is headers, not file data. Over Ethernet with a 1,500-byte MTU, TCP/IPv4 carries 1,460 bytes of data in every 1,538 bytes on the wire, a 5.1% loss.
That is where a 5% allowance comes from. With the 12-byte TCP timestamp option, the data drops to 1,448 bytes, a 5.9% loss.
The server's own upload limit, Wi-Fi signal strength and other devices sharing the line slow a transfer further, so treat any estimate as a best case.
Common mistakes
- Reading Mbps as MB/s. The estimate comes out eight times too short.
- Counting overhead twice. A speed measured as file throughput, such as a browser's MB/s figure, already excludes headers, so use 0% with it.
- Entering the full size of a resumed download. Only the part left to transfer counts.
- Forgetting install time. Unpacking, verifying and installing happen after the transfer and add to the wait.
Typing sizes, speeds and overhead
- Speeds can be kbit/s, Mbit/s, Gbit/s or MB/s; Mbps is the same as Mbit/s.
- Sizes can be decimal MB, GB and TB or binary MiB, GiB and TiB.
- Overhead is a percentage from 0 to 99, where 0 uses the raw line rate.
Related tools
To convert rates or sizes on their own, use the data transfer rate converter or the data storage converter. The bandwidth calculator works out how much data a link moves in a set time.
Worked examples
1 GB at 100 Mbit/s, no overhead
- File size
- 1 GB
- Connection speed
- 100 Mbit/s
- Protocol overhead
- 0%
- Download time
- 1 min 20 s
- Time in seconds
- 80 s
Checked against: 8 × 10⁹ / 10⁸ = 80 s
1 GiB at 1 Gbit/s (binary size, decimal speed)
- File size
- 1 GiB
- Connection speed
- 1 Gbit/s
- Protocol overhead
- 0%
- Time in seconds
- 8.58993 s
Checked against: 2³⁰ × 8 bits / 10⁹ bit/s = 8.589934592 s
4.7 GB DVD image at 25 Mbit/s with 10 % overhead
- File size
- 4.7 GB
- Connection speed
- 25 Mbit/s
- Protocol overhead
- 10%
- Time in seconds
- 1,671.11 s
Checked against: 4.7 × 8 × 10⁹ / (25 × 10⁶ × 0.9) ≈ 1671.11 s
Questions
How long does it take to download 1 GB at 100 Mbps?
About 84 seconds with 5% protocol overhead, or 80 seconds at the raw line rate. 1 GB is 8,000 megabits, and 8,000 ÷ 100 = 80 s. Halving the speed doubles the time: 160 s raw at 50 Mbps. At 1 Gbps the same gigabyte takes 8 s raw, about 8.4 s with overhead.
What is the difference between Mbps and MB/s?
Mbps (megabits per second) is how connection speeds are sold; MB/s (megabytes per second) is how browsers and download managers show progress. A byte is 8 bits, so divide Mbps by 8: a 100 Mbps line moves at most 12.5 MB/s, and about 11.9 MB/s after 5% overhead. Both use decimal prefixes, so 1 Mbit = 10⁶ bits (NIST).
Why is my download slower than my internet speed?
Part of every packet is headers, not your file. With a 1,500-byte Ethernet MTU, TCP/IPv4 carries 1,460 bytes of data in every 1,538 bytes on the wire (IEEE 802.3 framing plus 20-byte IP and TCP headers), a 5.1% loss; the 12-byte TCP timestamp option cuts the data to 1,448 bytes, 5.9%. Beyond that, the server's upload limit, Wi-Fi signal and other devices sharing the line slow it further.
Why does a 50 GB download show as 46.6 GB on my computer?
Because Windows File Explorer counts in binary units but labels them GB: it divides by 2³⁰ (1,073,741,824) bytes, so 50 × 10⁹ bytes appears as 46.6 GB. Stores and ISPs use decimal gigabytes (10⁹ bytes, IEC 80000-13), and macOS has shown decimal sizes since Mac OS X 10.6 in 2009. Choose GiB in the size field for a size copied from Windows.
About this calculator
Sources
- NIST — Prefixes for binary multiples (IEC 80000-13): 1 byte = 8 bits, GB vs GiB
- IEEE 802.3 Ethernet framing (1,500-byte MTU + 38 bytes of preamble, header, FCS and gap) with RFC 791 / RFC 793 20-byte IPv4 and TCP headers
Checked against references
This calculator includes 5 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.