Network rates are normally written in bits per second, while file sizes are written in bytes. Eight bits equal one byte, so 100 Mb/s is a theoretical 12.5 MB/s before protocol, radio, storage, server and congestion effects. Enter a file size, rate and measured or planning throughput percentage to see both the ideal and adjusted transfer time.
Convert network rate and estimate transfer time
Use a decimal network rate and choose the file-size unit explicitly. The throughput percentage makes real-world planning assumptions visible.
Use bits, bytes and time without mixing units
| Result | Formula | Boundary |
|---|---|---|
| Theoretical MB/s | decimal bits per second ÷ 8 ÷ 1,000,000 | No protocol or device overhead |
| Ideal seconds | file bytes × 8 ÷ bits per second | Assumes the stated rate is sustained |
| Adjusted seconds | ideal seconds ÷ throughput fraction | Uses your planning or measured percentage |
| Binary file size | GiB × 1,073,741,824 bytes | GiB is not the same quantity as GB |
Why a link rate is not a delivered file rate
A router, Wi-Fi standard or broadband plan can describe a link or access rate without guaranteeing one file transfer at that rate. Protocol headers, retransmissions, shared radio time, signal quality, server capacity, storage speed, encryption, application behavior and other traffic can reduce useful throughput.
For planning, use a percentage based on a representative measured transfer when possible. One speed-test result does not prove sustained performance to every destination, and this calculator does not diagnose latency, jitter or packet loss.
Plan with representative evidence
- Confirm whether the source rate is a link rate, an internet-plan rate or measured application throughput.
- Use the actual file-size unit: decimal GB or binary GiB.
- Repeat a representative transfer at the time and location that matter.
- Record wired or wireless path, device, server, signal and competing traffic.
- Treat large differences as a diagnostic starting point, not proof that one component is faulty.
Sources and further reading
Technical statements were reviewed against these references. External pages may change after our review date.
- Definitions of the SI units: The binary prefixes — National Institute of Standards and Technology
- The International System of Units: SI prefixes — Bureau International des Poids et Mesures