Numbers, Bitwise & Units
Estimate duration from size and speed, or find the bandwidth needed to meet a deadline.
1 B = 8 bit · 1 GB = 1000³ B · 1 GiB = 1024³ B. Mbps uses decimal bits; MB/s uses decimal bytes.
Use a dot, up to 15 significant digits, and values from 0.000000000001 to 1000000000000000. Units go in the selectors.
Estimated duration
≈ 800 s
80000000000 bit ÷ 100000000 bps ≈ 800 s
100000000 bps × (100 ÷ 100) ≈ 100000000 bps
80000000000 bit ÷ 100000000 bps ≈ 800 s
Constant average throughput; no setup latency or separate disk time. All values are estimates rounded to 10 significant digits.
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Payload rate = entered rate × efficiency / 100. Use 100% for already measured payload throughput; lower it only for additional losses.
Estimate updated. Review the assumptions before using it.
Use the transfer time calculator before scheduling a backup, moving a media archive or starting a large download. A quoted line speed is only one input: the size unit and the share of that speed available to your transfer matter too.
The same model serves as a download time calculator and an upload time calculator. Use the rate for the direction you intend to transfer. If you already measured sustained payload throughput, keep efficiency at 100% to avoid discounting that measured speed twice.
For 10 GB at 100 Mbps, the ideal duration is 800 seconds. At 80% efficiency it becomes 1000 seconds. Both figures remain visible, so the extra 200 seconds can be traced to your assumption. Losing 20% of the usable rate increases time by 25%, not by 20%.
This transfer time calculator also works as a bandwidth calculator. To move 10 GB in ten minutes, the payload must average about 133.3333333 Mbps. With 80% efficiency, the required line rate rises to about 166.6666667 Mbps. The target time stays fixed while the required capacity changes.
Choose GB for decimal gigabytes and GiB for binary gibibytes. A speed shown as MB/s is a byte rate; Mbps is a bit rate. Changing a selector reinterprets the number already in the field, rather than converting that number into a new unit.
An efficiency of 90 means 90% of the entered rate carries your data. It does not add 10% to the file size or predict a particular protocol. Start from 100% for measured payload speed and lower the percentage only when you want an additional allowance.
Turning automatic calculation off reveals the Calculate button; Ctrl/Cmd+Enter also runs it. Changes immediately disable export until results refresh. The report includes the active input pair, efficiency and substituted formula, so someone reading it later can reproduce your estimate.
Time mode divides data bits by effective bits per second. Bandwidth mode divides data bits by the target seconds and efficiency. Separate speed and duration drafts survive mode changes; a hidden draft does not become an extra constraint or leak into the report.
Capacity supports bit, B, KB through PB and KiB through PiB. Speed includes bps through Tbps, decimal byte rates through TB/s and binary byte rates through TiB/s. The result shows useful payload throughput in both Mbps and MB/s, making the factor of eight easy to verify.
Expand equivalent units for seconds, minutes, hours and days, or the required rate in fourteen speed units. The formula uses normalized bits and seconds. Display values use ten significant digits; scientific notation keeps very small positive estimates visible instead of rounding them to zero.
Convert the amount to bits, then divide by usable bits per second. Ten decimal gigabytes contains 80000000000 bits; at 100000000 bits per second it takes 800 seconds. When efficiency is below 100%, multiply the rate by the efficiency fraction before dividing.
There are eight bits in one byte. A 100 Mbps rate therefore equals 12.5 MB/s before additional losses. Select the unit that the source actually displays; entering 100 MB/s describes a connection eight times faster than 100 Mbps.
The transfer may share bandwidth, run into a server limit or wait for storage and processing. A fixed-rate estimate cannot predict those changes. Use a measured average or compare several efficiency assumptions, while keeping installation and decompression time separate.
Headers, acknowledgments and retransmissions use resources beyond the file payload. This page represents their combined effect only through your chosen efficiency. For a 10% rate loss, enter 90%; the duration is divided by 0.9 rather than multiplied by 1.1.
Many access plans allocate different rates to the two directions. For a cloud backup, enter the upstream rate instead of the advertised downstream rate. The formula stays the same; the connection rate and available share can be very different.
Something looks wrong?
Return to the transfer time calculator, compare an ideal baseline with your own efficiency assumption, and export the result with its formula.