Compute transfer time, maximum file size or required bandwidth from file size and network speed, with decimal and binary units.
Enter the file size and your bandwidth to see the transfer time.
Enter a positive number.
Enter a positive number.
Enter a positive number.
File size presets
Bandwidth presets
90%
Accounts for TCP overhead, latency and protocol losses. Set to 100% for theoretical maximum.
Transfer time
time = size ÷ (speed × efficiency)
Quick reference: download time at common speeds
Speed
1 GB
10 GB
50 GB
10 Mbps DSL
~15 min
~2 h 27 min
~12 h
25 Mbps
~5 min 56 s
~59 min
~4 h 56 min
100 Mbps cable
~1 min 29 s
~14 min 49 s
~1 h 14 min
500 Mbps Wi-Fi 5
~17 s
~2 min 58 s
~14 min 49 s
1 Gbps fiber
~8.9 s
~1 min 29 s
~7 min 24 s
Values include a 90% real-world efficiency factor.
Frequently asked questions
What is the difference between Mbps and MB/s?
Mbps means megabits per second, MB/s means megabytes per second. 1 byte equals 8 bits, so 1 MB/s equals 8 Mbps. A 100 Mbps connection delivers at most 12.5 MB/s. ISPs advertise bandwidth in bits per second; file managers and operating systems display transfer speed in bytes per second. Always check the unit before comparing.
Why does my file size show differently in the OS and on the label?
Storage vendors use decimal units: 1 GB = 1,000,000,000 bytes. Windows and most tools display binary units: 1 GiB = 1,073,741,824 bytes. A 1 TB drive is labelled with a decimal terabyte and shows as roughly 931 GiB in the OS. This calculator supports both families so you can compute against either convention.
Why does the real download time differ from the theoretical value?
Theoretical throughput assumes the full nominal link speed is used by the payload. In practice, TCP/IP, TLS and HTTP add header overhead, latency reduces throughput on long links, Wi-Fi loses frames, and ISPs may throttle during peak hours. A typical real-world efficiency is 85 to 95 percent of the rated speed. Move the slider to match your environment.
Should I use decimal (MB, GB) or binary (MiB, GiB) units?
Use decimal when the source specifies decimal, for example storage capacity, cloud pricing and most network specifications. Use binary when the source is memory, OS file managers or software that reports sizes in KiB, MiB, GiB or TiB. Mixing the two causes small discrepancies, around 7 percent at the terabyte scale.
How do I figure out what bandwidth I need for a 4K video stream?
Switch to the Required speed mode, enter the file or session size and the acceptable duration. For a 25 GB 4K movie watched in 2 hours, the required sustained rate is about 27.8 Mbps before overhead, or roughly 31 Mbps at 90 percent efficiency. Live 4K streams usually need 25 to 50 Mbps depending on the codec and bitrate.
Can I compute the maximum file I can transfer in a given time?
Yes. Switch to Max size mode, enter your bandwidth and the available time window. The calculator multiplies speed by duration and applies the efficiency factor. This mode is useful for backup windows, mobile data limits and bandwidth-capped plans.
Results are estimates based on the entered bandwidth and efficiency factor. Real-world transfer times depend on server load, routing, Wi-Fi conditions and protocol overhead.
This tool converts between file size, bandwidth and transfer duration across three calculation modes. Enter a file size and your link speed to see how long a download or upload will take. Switch to Max size mode to find out the largest file you can move within a given time window, useful for backup schedules and mobile data caps. Switch to Required speed mode to compute the minimum bandwidth needed to transfer a file within a target duration.nnSupported units include decimal bytes (B, KB, MB, GB, TB) and binary bytes (KiB, MiB, GiB, TiB), plus bit-based speeds (bps, kbps, Mbps, Gbps) and byte-based speeds (KB/s, MB/s, GB/s). A real-world efficiency slider defaults to 90 percent to account for TCP overhead, latency and protocol losses; set it to 100 percent for the theoretical maximum.nnExample: a 25 GB 4K movie over a 200 Mbps 5G link at 90 percent efficiency takes about 18 minutes 31 seconds. A 50 GB game over 1 Gbps fiber takes about 7 minutes 24 seconds. Use the bandwidth and file-size presets to explore dial-up, DSL, 4G, 5G, Wi-Fi and fiber scenarios.