File Transfer Time Calculator
Enter a file size and a connection speed to calculate how long an upload or download will take, correctly handling the bits-vs-bytes mix-up.
Estimated transfer time
13 min 20 sec
10 GB at 100 Mbps, at full speed with no overhead
This assumes the full connection speed is used for the whole transfer, with no other traffic competing for bandwidth and no protocol overhead — real transfers are usually somewhat slower than this theoretical figure. Connection speeds (Mbps, Gbps) are almost always quoted in bits per second, while file sizes are almost always shown in bytes (MB, GB) — 1 byte = 8 bits, and this calculator converts between them automatically so you don't have to.
About this tool
How to use it
- Enter the file size and pick its unit (MB, GB, or TB).
- Enter your connection speed and pick its unit (Mbps or Gbps) — check your plan, router, or a speed test if you don't know it.
- Press Calculate Transfer Time, or just keep typing — the result updates live.
- Treat the result as a best case — real transfers are usually somewhat slower once overhead and other traffic are accounted for.
Why it matters
Connection speeds are almost always advertised in bits per second (Mbps, Gbps), but file sizes are almost always shown in bytes (MB, GB) — and 1 byte is 8 bits. Dividing a file size in bytes directly by a speed in bits, without converting, gives an answer 8 times too fast, which is the single most common mistake people make estimating a transfer time by hand.
When to use it
Useful before starting a large upload or download and wanting to know roughly how long to wait, when comparing how much faster a plan upgrade would actually make transfers, or when explaining to someone else why their download is taking as long as it is.
Good to know
This calculates a theoretical best-case time: the full connection speed, dedicated entirely to this one transfer, with no protocol overhead and no other traffic competing for bandwidth. Real-world transfers are typically slower than this figure, sometimes considerably so on a shared or congested connection. File size units here use decimal (SI) definitions — 1 MB = 1,000,000 bytes, 1 GB = 1,000,000,000 bytes — matching how file sizes and connection speeds are conventionally advertised.
Common questions
Why is my actual transfer slower than the calculated time?
This calculates a theoretical best case — your full connection speed dedicated entirely to one transfer, with zero overhead. Real transfers share bandwidth with other traffic, lose some throughput to protocol overhead, and can be limited by the server or service on the other end, so actual speeds are typically somewhat below the advertised maximum.
Why do bits and bytes matter here?
Internet connection speeds are conventionally quoted in bits per second (a 100 Mbps connection), while file sizes are conventionally shown in bytes (a 10 GB file). Since 1 byte equals 8 bits, mixing the two up without converting gives an answer that's off by a factor of 8 — this calculator does that conversion automatically.
What's the difference between Mbps and MB/s?
Mbps is megabits per second (a connection speed unit); MB/s is megabytes per second. A 100 Mbps connection transfers at roughly 12.5 MB/s at best (100 ÷ 8), which is why a '100 Mbps' plan feels much slower in file-size terms than the number alone suggests.
Does this account for upload versus download speed differences?
No — enter whichever speed (upload or download) is relevant to the direction you're calculating. Many connections have different upload and download speeds, so use the correct one for the direction of the transfer you're estimating.