How do I calculate download time?

Convert file size to bits, divide by bits per second, then adjust for real-world efficiency or overhead.

Why is 100 Mbps not 100?

Mbps uses bits and uses bytes. One byte has 8 bits, so 100 Mbps is about 12.5 before overhead.

Does this test my internet speed?

No. It estimates transfer time from numbers you enter; it is not a live speed test.

Download Time Calculator

Estimate download or upload time from file size and internet speed, or calculate the speed needed to finish a transfer on time.

This calculator does not run a live speed test. Enter a plan speed or measured result to estimate file transfer time and compare Mbps with MB/s.

Direction

File size

File size unit

Download speed

Speed unit

Efficiency / overhead allowance

Estimate file transfer time

English download-time intent is calculator-first: enter a file size and connection speed, then estimate how long a download or upload may take.

t im e (s) = \frac{f i l e s i z e ( b y t es ) \times 8}{s p ee d ( bi t s / s ) \times e f f i c i e n cy}

Calculator, not a live speed test

This page does not measure your connection. Use your internet plan or a speed-test result, then estimate transfer time here.

Mbps and are different

1 b y t e = 8 bi t s

100 M b p s \approx 12.5 M B / s

Internet plans are usually advertised in megabits per second, while browsers often show megabytes per second. Real transfers can be slower because of Wi-Fi, server limits, congestion and protocol overhead.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

Related Tools

Unit Converter

Convert common units for length, mass, temperature, area, volume, speed, data, pressure, energy, power, time, angles and fuel economy.

Open

Base64 Encoder and Decoder

Encode UTF-8 text to Base64 or decode Base64 and Base64URL strings back to text in your browser.

Open

UUID Generator

Generate UUID v4 and GUID-style identifiers in bulk, with uppercase, no-dash, and brace formatting options.

Open

Time Calculator

Add and subtract time durations in HH:MM:SS, HH:MM or unit format, with decimal hours, total minutes, total seconds and copyable results.

Open