01

Bits and bytes are different units

Internet plans quote bits; files usually show bytes.

Eight bits make one byte. Decimal GB and binary GiB are also different. State the unit before calculating so an apparent shortfall is not a notation mistake.

02

Calculate the theoretical floor

File bits divided by megabits per second gives seconds.

A 1 GB decimal file contains 8,000 megabits, so 100 Mbps needs at least 80 seconds. That result assumes the full entered rate carries file payload.

03

Expose overhead instead of hiding it

Protocols, Wi-Fi, server limits, and congestion reduce payload rate.

Use an efficiency assumption or, better, enter observed throughput. The calculator states its assumption and never promises an exact completion time.

04

Measure the bottleneck that matters

Latency and throughput serve different experiences.

Bulk downloads depend strongly on sustained throughput, while calls and games also depend on latency, jitter, and loss. A single “fast” label cannot summarize both.

CT TOOL / 02

Turn Mbps into time.

Compare the theoretical floor with an explicit effective-rate assumption.

Formula: file megabits ÷ (Mbps × effective-rate assumption). Server, Wi-Fi, protocol, and congestion limits remain outside the formula.

RESULTEnter the observations to calculate.
Method: NIST binary-unit definitions ↗

QUESTIONS THIS ANSWERS

Questions this answers

  • How long will a 100 GB download take?
  • Why is my file transfer slower than my internet plan?

Found something wrong? Report an error or read the corrections policy.

2 SOURCESEvidence ledger

Sources

  1. 01
    Prefixes for Binary Multiples ↗

    National Institute of Standards and Technology · accessed 31 Aug 2026

  2. 02
    Broadband Speed Guide ↗

    Federal Communications Commission · accessed 31 Aug 2026