Download Time Calculator
Enter a file size and your download speed to find out exactly how long the download will take. Switch between metric (MB, GB, TB) and binary (MiB, GiB, TiB) file sizes, pick any common speed unit (Kbps through Gbps, or MB/s), and the result updates instantly. Flip to reverse mode to find out what speed you need to finish a download in a target time.
Formula
Worked example
A 4 GB game download over a 100 Mbps connection: 4 GB = 4 × 1,000,000,000 × 8 = 32,000,000,000 bits. 100 Mbps = 100,000,000 bps. Time = 32,000,000,000 / 100,000,000 = 320 seconds = 5 min 20 sec. With 5% TCP overhead, effective speed is 95 Mbps and time rises to about 5 min 37 sec.
How download time is calculated
Download time is calculated by dividing the total file size in bits by your connection speed in bits per second. The key conversion is that 1 byte equals 8 bits, which is why a 100 MB file is 800 megabits. Internet providers advertise speeds in megabits per second (Mbps), while file sizes are usually displayed in megabytes (MB), so the unit mismatch trips up many people. Once you have the file size in bits and the speed in bits per second, the formula is simply: time = file size / speed. This calculator handles all the unit conversions automatically, whether you choose metric units (MB, GB, TB based on powers of 1,000) or binary units (MiB, GiB, TiB based on powers of 1,024).
Why real downloads are slower than the estimate
Advertised broadband speeds are theoretical maximums, and actual downloads typically fall short for several reasons. TCP/IP and HTTP headers add 5-10% overhead on most connections. Wi-Fi signal attenuation, interference from neighboring networks, and competing devices on your LAN all reduce effective throughput. The server you are downloading from may also be the bottleneck: a slow CDN edge node or an overloaded origin server will cap your speed regardless of how fast your ISP connection is. VPNs introduce additional encryption overhead, typically 10-20%. The protocol overhead selector in this calculator lets you add a realistic deduction so the estimate matches real-world conditions.
Metric vs. binary file sizes
Hard drive manufacturers and storage card makers use metric prefixes where 1 GB = 1,000,000,000 bytes. Operating systems have historically used binary prefixes where 1 GiB = 1,073,741,824 bytes (2 to the 30th power). This creates a visible mismatch: a drive advertised as 1 TB shows up as about 931 GiB in Windows or macOS. The International Electrotechnical Commission resolved this in 1998 by standardising the binary prefixes (kibibyte, mebibyte, gibibyte, tebibyte), but colloquial usage of KB, MB and GB still varies. If you are unsure which system your file manager uses, selecting the "MiB/GiB/TiB" options in this calculator will give the more conservative (larger) estimate.
Reverse mode: finding the speed you need
Sometimes the question is not "how long will this take?" but "what speed do I need to finish by a deadline?" Flip the mode selector to "Find required speed" and enter your file size and the time limit. The calculator divides the file size in bits by the time in seconds to find the minimum bits-per-second throughput, then converts that to the most readable unit. Remember to account for overhead: if your target is 10 minutes and there is 10% overhead, you actually need a plan rated 11% faster than the ideal calculation suggests.
Typical download times by connection and file size
| File size | 10 Mbps | 100 Mbps | 1 Gbps |
|---|---|---|---|
| 10 MB | 8 sec | 0.8 sec | 0.08 sec |
| 100 MB | 1.3 min | 8 sec | 0.8 sec |
| 1 GB | 13.3 min | 1.3 min | 8 sec |
| 4 GB | 53 min | 5.3 min | 32 sec |
| 25 GB | 5.6 hr | 33 min | 3.3 min |
| 50 GB | 11 hr | 1.1 hr | 6.7 min |
| 100 GB | 22 hr | 2.2 hr | 13 min |
Estimated times using ideal throughput (no overhead). Actual times will be longer.
Frequently asked questions
Why is my actual download speed lower than my internet plan?
ISP plans advertise peak speeds under ideal conditions. Real throughput is reduced by Wi-Fi attenuation, router firmware, the number of devices on your LAN, server capacity at the source, peak-hour congestion on the ISP network, and TCP/IP protocol overhead (typically 5-10%). For accurate estimates, run a speed test immediately before downloading and use that result rather than your plan's advertised maximum.
What is the difference between Mbps and MB/s?
Mbps (megabits per second) is the unit ISPs use to rate internet connections. MB/s (megabytes per second) is what download managers and operating systems typically show. Because 1 byte = 8 bits, a 100 Mbps connection delivers a maximum of 12.5 MB/s. If your speed test says 100 Mbps and your download manager shows ~12 MB/s, that is correct and expected.
How long does it take to download a 1 GB file?
On a 100 Mbps connection: 1 GB = 8,000 megabits; 8,000 / 100 = 80 seconds, about 1 minute 20 seconds under ideal conditions. With 5% TCP overhead the effective speed drops to 95 Mbps and the time rises to roughly 84 seconds. On a 25 Mbps connection the same file takes about 5.5 minutes; on a 1 Gbps fiber connection it takes about 8 seconds.
What is the difference between MB (megabyte) and MiB (mebibyte)?
1 MB = 1,000,000 bytes (powers of 10, used by storage manufacturers and most network equipment). 1 MiB = 1,048,576 bytes (powers of 2, historically used by operating systems). The gap is about 4.9% at the megabyte level but grows to nearly 10% at the gigabyte level. For download time calculations the difference is small, but choosing the wrong unit will cause a proportional error in your estimate.
How can I speed up a slow download?
Use a wired Ethernet connection instead of Wi-Fi if possible, as it eliminates wireless interference and halving overhead. Move closer to the router or use a Wi-Fi 6/6E router. Close other applications and browser tabs that are using bandwidth. Schedule large downloads during off-peak hours (late night or early morning) when ISP congestion is lowest. Use a download manager that supports multi-threaded connections to the same server. Check that your router firmware is up to date, as outdated firmware often limits throughput.
How do I calculate the time to download a game that is 50 GB?
Enter 50 in the file size field, select GB as the unit, and enter your speed and unit. For example, on a 200 Mbps cable connection: 50 GB = 400,000 megabits; 400,000 / 200 = 2,000 seconds = about 33 minutes and 20 seconds. Adding 5% TCP overhead raises this to about 35 minutes. Use the reference table below for a quick comparison across common speeds.