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Upload Time Calculator

Estimate a transfer time from file size and connection speed.

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%

Real transfers rarely reach the advertised speed. If you have measured yours, enter it here.

%

Protocol overhead adds to what must be sent. Leave this at 0 for the payload alone, or enter a value you have measured.

Transfer time

1:06:40
66.6667 min · 1 h 6 min 40 s
Effective speed
20.000 Mbps
Data actually transferred
10.00 GB
Estimated completion offset
1 h 6 min 40 s

How this is calculated

Protocol overhead is added to the file size to give the bytes actually sent, which are turned into bits. The connection speed is reduced by the efficiency you enter, and the bits are divided by that effective speed.

bytesToSend     = fileSizeBytes × (1 + overheadFraction)
bitsToSend      = bytesToSend × 8
effectiveBps    = connectionBps × efficiencyFraction
durationSeconds = bitsToSend / effectiveBps

Units

Speed is held in bits per second, file size in bytes and duration in seconds. One byte is eight bits everywhere, which is why a byte-based speed such as MB/s is multiplied by eight the moment you enter it. File sizes are decimal by default: 1 GB is 1,000,000,000 bytes.

Assumptions

  • The connection holds the stated speed for the whole transfer.
  • Efficiency is 100% unless you set it, because any other default would be an invented measurement.
  • The answer is a duration, never a completion time: nothing on this site reads a clock.

Read how every number on this site is derived.

Worked example

A 10 GB export over a 20 Mbps connection at 100% efficiency:

bytesToSend     = 10,000,000,000 × (1 + 0)      = 10,000,000,000 bytes
bitsToSend      = 10,000,000,000 × 8            = 80,000,000,000 bits
effectiveBps    = 20,000,000 × 1.00             = 20,000,000 bps
durationSeconds = 80,000,000,000 ÷ 20,000,000   = 4,000 s
minutes                                         = 66.6667 min
clock                                           = 1:06:40

This is test vector V4 in the calculator requirements. At 80% efficiency the same transfer takes exactly 5,000 seconds, which is why the efficiency field is worth measuring once.

Frequently asked questions

Why is my upload slower than my connection speed suggests?

Connections are advertised in bits per second and files are measured in bytes, so a 20 Mbps link moves about 2.5 MB each second at best. Real transfers also lose throughput to protocol overhead, contention, distance to the server and the upload limit of your plan. Use Efficiency under Advanced to enter the share you have measured.

What is the difference between Mbps and MB/s?

A megabit per second is one million bits per second; a megabyte per second is one million bytes, which is eight million bits. The unit selector accepts either, and both are converted to bits per second before the calculation, so the answer is the same whichever you choose.

Does this work for downloads?

Yes. The arithmetic for a transfer in either direction is identical, so enter your download speed instead. The tool is labelled for upload because that is the direction most creators are constrained by.

Why does it not tell me what time the upload will finish?

The calculation reads no clock, so it can only state a duration. Add the duration shown to the time you actually start, and remember that a transfer paused or throttled part way through will not follow it.

Should I add protocol overhead?

Leave it at 0 unless you have measured it. Protocol overhead adds to what must be sent, so it multiplies the payload here rather than dividing it. Most creators get a closer estimate by lowering Efficiency instead, since that also covers contention and server-side limits.