Download Time
Calculate how long a download will take based on file size and internet speed.
About Download Time
Download time is the file size converted to bits divided by the effective download speed. ISPs advertise speed in megabits per second (Mbps) while file sizes are usually shown in megabytes (MB), so the file size is first multiplied by 8 to convert MB to megabits. Real-world throughput is typically lower than the advertised link speed due to TCP/IP overhead, server limits, and network congestion, which the efficiency factor accounts for.
Formula
Download time
time = (file_size_MB × 8) / (download_speed_Mbps × efficiency)
- S_MB
- File size in megabytes
- v_Mbps
- Download speed in Mbps
- \eta
- Real-world efficiency factor
Worked example
With the default values below, Download Time returns Estimated Download Time of 1m 34.1s. Change any input above and every figure here is recalculated in your browser.
Inputs used
- File Sizeminimum 0 MB
- 1,000 MB
- Download Speedminimum 0.1 Mbps
- 100 Mbps
- Real-World Efficiencyaccepts 10–100
- 85
Results
- Estimated Download Time
- 1m 34.1s
- Ideal Time (100% speed)
- 1m 20s
- Effective Speed
- 85.00 Mbps
- Time in Seconds
- 94.12 s
Step by step
- 1Values used
- 2Download time
- 3Estimated Download Time= 1m 34.1s
- 4Ideal Time (100% speed)= 1m 20s
- 5Effective Speed= 85.00 Mbps
- 6Time in Seconds= 94.12 s
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why is my download slower than my advertised internet speed?
ISPs advertise the theoretical maximum link speed in Mbps, but actual throughput is reduced by TCP/IP overhead, Wi-Fi interference, server-side bandwidth limits, and congestion at any hop between you and the source. The efficiency field lets you model this real-world drop, typically 70-95% of the rated speed.
Why multiply the file size by 8?
File sizes are conventionally shown in bytes (MB, GB) while connection speeds are marketed in bits per second (Mbps). Since 1 byte = 8 bits, the file size in megabytes must be multiplied by 8 to get megabits before dividing by a Mbps speed.
How can I speed up a large download?
Use a wired Ethernet connection instead of Wi-Fi, download from a server geographically closer to you or with a CDN, avoid other devices saturating the same link during the transfer, and check whether the source server itself is rate-limiting the connection.