Quick answer
Time to download a file at a given speed. Enter file size, size unit, connection speed and speed unit and a few more values and the download time calculator returns time and seconds.
Related tools: Bandwidth Calculator: Bandwidth needed to move a file in a given time. Data Transfer Calculator: Amount of data moved at a speed over a time. Media File Size Calculator: File size of an audio or video stream from its bitrate and duration.
How to use the Download Time Calculator
- Enter file size (above 0).
- Choose size unit: kB, MB, GB, TB, KiB and MiB and 2 more.
- Enter connection speed (above 0).
- Choose speed unit: kbit/s, Mbit/s, Gbit/s, MB/s and GB/s.
- Enter real-world efficiency (%) (between 0 and 100). It starts at 100.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| File size | A number | > 0 |
| Size unit | Choose one: kB; MB; GB; TB; KiB; MiB; GiB; TiB | Starts at GB |
| Connection speed | A number | > 0 |
| Speed unit | Choose one: kbit/s; Mbit/s; Gbit/s; MB/s; GB/s | Starts at Mbit/s |
| Real-world efficiency | A number, in % | > 0, ≤ 100, starts at 100 |
Formula and method
Formula
time = size × 8 ÷ (speed × efficiency)
IEEE-754 double precision; shown to the decimals indicated.
Protocol overhead and congestion usually keep real throughput below the line rate, so lower the efficiency to be realistic.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: File size = 4.7; Size unit = GB; Connection speed = 100; Speed unit = Mbit/s; Real-world efficiency = 100.
| Result | Value |
|---|---|
| Time | 0:06:16 |
| Seconds | 376 |
Example 2
Inputs: File size = 700; Size unit = MB; Connection speed = 8; Speed unit = Mbit/s; Real-world efficiency = 80.
| Result | Value |
|---|---|
| Time | 0:14:35 |
| Seconds | 875 |
Example 3
Inputs: File size = 1.5; Size unit = TiB; Connection speed = 250; Speed unit = MB/s; Real-world efficiency = 90.
| Result | Value |
|---|---|
| Time | 2:02:10 |
| Seconds | 7,330.1 |
The first line is the headline result (time). Below it the download Time Calculator lists seconds, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Megabits versus megabytes
Internet speeds are quoted in megabits per second (Mbps), file sizes in megabytes or gigabytes. There are 8 bits in a byte, so a 100 Mbps connection moves at most 12.5 megabytes per second. Real downloads are slower than the line rate because of protocol overhead, so lower the efficiency to be realistic.
A 4.7 GB file at different connection speeds
Every figure in this table comes from running this calculator, so it matches what the form returns.
| Speed (Mbps) | Time | Seconds |
|---|---|---|
| 10 | 1:02:40 | 3,760 |
| 50 | 0:12:32 | 752 |
| 100 | 0:06:16 | 376 |
| 500 | 0:01:15 | 75.2 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- File size: entering "0" shows "File size must be greater than 0." beside that field and no result.
- Connection speed: entering "0" shows "Connection speed must be greater than 0." beside that field and no result.
Choosing between the Download Time Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Bandwidth Calculator](/technology/bandwidth-calculator/) | data size, size unit and time allowed | Bandwidth required |
| [Data Transfer Calculator](/technology/data-transfer-calculator/) | speed, speed unit and duration | Data transferred |
| [Media File Size Calculator](/technology/file-size-calculator/) | bitrate, bitrate unit and hours | File size |
| [Bitrate Calculator](/technology/bitrate-calculator/) | file size, size unit and duration | Average bitrate |
| [Upload Time Calculator](/technology/upload-time-calculator/) | file size, size unit and connection speed | Time |
Background: networking and display
Network speeds are quoted in bits per second and file sizes in bytes, and a byte is 8 bits, so a 100 Mbps link moves at most 12.5 megabytes per second; real throughput is usually below the advertised rate. Pixel density is the diagonal in pixels divided by the diagonal in inches: a 1920×1080 display of 24 inches is about 92 pixels per inch, and a 3840×2160 display of 27 inches about 163.
Assumptions and limitations
- Real speeds vary
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for file size and connection speed to confirm this.
Frequently asked questions
What does the Download Time Calculator calculate?
Time to download a file at a given speed. It returns Time and Seconds.
What formula does the Download Time Calculator use?
time = size × 8 ÷ (speed × efficiency). Protocol overhead and congestion usually keep real throughput below the line rate, so lower the efficiency to be realistic.
What do I need to enter in the download Time Calculator?
You enter File size, Size unit, Connection speed, Speed unit and Real-world efficiency (%).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Real speeds vary.
What does the “Size unit” option change?
It sets how the download Time is worked out. The choices are kB, MB, GB, TB, KiB, MiB, GiB and TiB.
What is an example of a download Time result?
With file size 4.7, size unit GB, connection speed 100, speed unit Mbit/s and real-world efficiency 100, the time is 0:06:16.
Related calculators
- Bandwidth Calculator — Bandwidth needed to move a file in a given time.
- Data Transfer Calculator — Amount of data moved at a speed over a time.
- Media File Size Calculator — File size of an audio or video stream from its bitrate and duration.
- Bitrate Calculator — Average bitrate of a file from its size and duration.
- Upload Time Calculator — Time to upload a file at a given speed.
- IP Subnet Calculator — IPv4 network, broadcast, mask and host range from an address and CIDR prefix.
- Latency to Distance Calculator — Approximate one-way distance from round-trip latency.
- Network Throughput Calculator — Maximum TCP throughput from window size and round-trip time.
- Mining Time Estimate Calculator — Expected time to find a proof-of-work block.
Sources
- SI prefixes (kB = 1,000 B) and IEC prefixes (KiB = 1,024 B); 8 bits per byte
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.