Tech
Download Time Calculator
Estimate how long a file will take to download from its size and connection speed. Supports binary or decimal sizes, Mbps/Gbps speeds, and a TCP/IP overhead.
Download time calculator
Size of the file you want to download.
ISPs quote speeds in bits per second. 100 Mbps is roughly 12.5 MB/s.
Drive vendors use decimal. Operating systems often display binary.
Accounts for TCP/IP headers and ACKs. 5% is a typical default; set to 0 to ignore.
Estimated download time
1 min 24 sec
84.21 seconds total
- File size
- 1 GB
- Line rate
- 100 Mbps
- Effective throughput
- 95 Mbps (11.88 MB/s)
- Overhead applied
- 5%
Same file on common connections
| Connection | Download time |
|---|---|
| Dial-up (56 Kbps) | 1 day 17 hr 46 min |
| DSL (5 Mbps) | 28 min 4 sec |
| Cable (100 Mbps) | 1 min 24 sec |
| Fiber (1 Gbps) | 8 sec |
All rows use the same file size, size convention, and protocol overhead as the inputs above.
Frequently Asked Questions about the Download Time Calculator
Why are connection speeds in bits per second but file sizes in bytes?
ISPs and network gear quote speed in bits per second by convention. File sizes are stored and shown in bytes. One byte is eight bits, so a 100 Mbps line is about 12.5 MB/s of raw throughput before any protocol overhead.
What is the difference between binary (1024) and decimal (1000) file sizes?
Drive vendors and most storage specs use decimal: 1 KB is 1,000 bytes, 1 GB is 1,000,000,000 bytes. Operating systems often display binary: 1 KiB is 1,024 bytes, 1 GiB is 1,073,741,824 bytes. A 1 GiB binary file takes about 7.4% longer to download than a 1 GB decimal file at the same speed.
Why does the calculator subtract a protocol overhead by default?
Real downloads never hit the full line rate. TCP and IP headers, ACK packets, and slow-start eat into useful bandwidth. A 5% default approximates a healthy wired connection. Set the overhead to 0 to see the theoretical best case, or raise it for lossy Wi-Fi and high-latency links.
Why does my real download speed look slower than this estimate?
The calculator uses your line rate, not your actual throughput. The server, your Wi-Fi link, congestion, TLS handshakes, throttling, and disk write speed can all cap the download well below your ISP rate. Try a wired connection and a fast mirror to get closer to the estimate.
Can I use this for upload time too?
Yes. Plug in your upload speed instead of download. The math is identical: bits transferred divided by effective bits per second. Just remember that residential connections often have much lower upload speeds than download.