Download Time Calculator
How long a file takes at a given connection speed.
Last updated
Your details
Protocol overhead and congestion mean you rarely get the full advertised speed.
Result
- Realistic download time
- 7 min 51 s
- Theoretical best case
- 6 min 40 s
- Effective transfer rate
- 10.63 MB/s
- File size in bytes
- 5,000,000,000
At 85% of the advertised speed
Megabits and megabytes
Internet plans are sold in megabits per second; files are measured in megabytes. Dividing by eight converts between them, so a 100 Mbps line tops out around 12.5 MB/s.
This single factor of eight is why downloads feel slower than the advertised number suggests. Nothing is wrong with the connection.
Why you never hit the theoretical speed
TCP/IP headers, retransmissions, encryption and the server's own limits all take a share. Wi-Fi adds contention and signal loss on top. Eighty to ninety percent of the line rate is a realistic expectation on a good wired connection; Wi-Fi is often lower.
For large transfers the bottleneck is frequently the source server or your storage device rather than the link itself.
What speed you actually need
Streaming standard definition takes about 3 Mbps, 1080p around 5 Mbps, and 4K between 15 and 25 Mbps. Video calls need 2 to 4 Mbps in each direction. Ordinary browsing and email barely register.
The number that matters for a household is concurrent demand, not headline speed. Four people streaming 4K simultaneously need roughly 100 Mbps; the same connection is idle most of the rest of the day.
Latency is not bandwidth
Bandwidth is how much data can move per second; latency is how long a single packet takes to make the trip. Video calls, gaming and general responsiveness depend far more on latency and jitter than on raw throughput.
This is why upgrading from 100 Mbps to 500 Mbps often changes nothing noticeable for everyday use. Large downloads finish faster; web pages do not load meaningfully sooner, because they were never bandwidth-limited.
Formula & methodology
What this calculator assumes
- Connection speeds are quoted in bits per second and file sizes in bytes, which is why a 100 Mbps line never delivers 100 MB per second. The ratio is eight before overhead and closer to nine after it.
- An overhead allowance accounts for TCP/IP framing, retransmission and protocol handshaking. Real throughput also depends on latency, congestion and the far end, none of which a size-over-speed calculation can see.
- Uses the decimal convention throughout: a megabyte is 10⁶ bytes, as the IEC standard and every ISP define it, not the 2²⁰ bytes an operating system reports.
Sources
Frequently asked questions
Why is my Wi-Fi slower than my plan?
Wi-Fi is a shared, half-duplex medium subject to interference, distance and competing devices. A wired test is the only way to check what your line actually delivers.
Why is my upload speed so much slower?
Most consumer connections are asymmetric by design, on the assumption that people download far more than they upload. Fibre connections are often symmetric; cable and DSL rarely are.
Does a faster router increase my speed?
Only if the router was the bottleneck. It cannot exceed what your line delivers, though a better router can improve Wi-Fi coverage and handle more simultaneous devices.