How to use (3 steps)
- Choose what to solve: transfer time (size + speed), transfer speed (size + time), or data size (speed + time).
- Enter the two known values with units. Turn on the efficiency factor if you want to account for overhead (e.g., 80%).
- Press Calculate or edit an input to update conversions. Use “Copy URL” to share exactly the same scenario.
Seconds in the display are rounded up; sizes and speeds are rounded to 2 decimals.
Inputs
Fill in any two fields (data size, transfer speed, transfer time). Keep units consistent with your entry: b = bit, B = byte (1B = 8b). Decimal (GB) and binary (GiB) units are both supported.
Results
Transfer time result
Estimated transfer time
1B = 8b. Decimal units use powers of 1000; binary units use powers of 1024.
How it’s calculated
- Formula: data size = transfer speed × time. When solving for speed or time, we just rearrange this equation.
- All inputs are converted to bits and seconds internally. Decimal units (GB) and binary units (GiB) are handled separately.
- If efficiency is on, effective speed = nominal speed × efficiency%. Use this to estimate protocol overhead or real-world loss.
- Seconds are rounded up for HH:MM:SS. Sizes and speeds are rounded to 2 decimals in the display.
- Real-world speeds fluctuate. Treat the output as an estimate, not a guarantee.
FAQ
What values do I need to enter?
Enter any two of size, speed, and time. The calculator computes the missing value automatically.
What is the difference between b and B?
b means bit, B means byte. One byte equals eight bits, so conversion mistakes can cause large errors.
Should I use GB or GiB?
Use GB for decimal SI units and GiB for binary IEC units. Choose the one used by your source system.
What does efficiency mean?
Efficiency accounts for protocol overhead and real-world conditions, so estimates are closer to observed speed.
Can I use this for backup windows?
Yes. It is useful for planning backup duration and network capacity before scheduling transfers.
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