Download time calculator

Estimate file transfer time from size and speed. Distinguish MB, MiB and Mbps and adjust transfer efficiency.

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Set your data

File size

File unit

Speed

Speed unit

Efficiency (%)

File size up to one trillion units; efficiency 1–100%. Assumes constant speed and does not test the network.

Result

Enter your values to see the result.

Download progress

Move the slider to compare elapsed and remaining time at a constant effective speed. The chart shows an estimate.

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How to use it

Convert the size to bits and divide by the bits transferred each second. Set an efficiency percentage for a more realistic scenario. MB and GB use decimal prefixes; MiB and GiB use powers of 1024 and are not interchangeable labels.

Move the slider to compare elapsed and remaining time at a constant effective speed. The chart shows an estimate.

Example inputs
Input	Result
1 GB; 100 Mbps; 80%	100 s

Method and limits

The estimate assumes constant speed. Network, server and device limitations may increase the time. This is not a speed test.

Example

Usage scenario

Input: 1 GB; 100 Mbps; 80%
Result: $\frac{8000000000}{80000000} = 100$

Calculation steps

Convert bytes to bits
$1000000000 \times 8 = 8000000000$
Apply efficiency to the speed
$100000000 \times 0.8 = 80000000$
Divide the size by the effective speed
$\frac{8000000000}{80000000} = 100$

As a mixed number

1 \frac{2}{3} \min

A 1 GB file contains eight billion bits. At 100 Mbps its ideal transfer takes 80 seconds. With 80% efficiency the usable rate is 80 Mbps and the estimated duration increases to 100 seconds.

What are the limits of this tool?

File size up to one trillion units; efficiency 1–100%. Assumes constant speed and does not test the network.

Inputs and results are processed in your browser and are not sent to the server. Aggregate statistics, when enabled, record only the tool and outcome, without the content.

Sources

NIST — Binary prefixes

PRACTICAL GUIDES

Mbps vs MB/s: understanding download time

Distinguish bits, bytes, decimal and binary units and advertised speed. Compare an estimated transfer time with a real download.

Follow the steps