## TL;DR

A really accurate speed test measures 100.8% of the advertised internet speed. This is due to safety margins taken (respectively +12% and -10%) when determining the internet speed.

Based on that knowledge and research, M-Lab appears to be the most accurate speed test there is, assuming 100.8 Mbps is the correct value to measure. This speed test has by far the smallest deviation from the download speed to be measured,

## Contents

## Introduction

Progressive insight shows that two speeds can be regarded as the correct value. These speed are:

- the true internet speed
- the advertised internet speed

### The true internet speed

The true internet speed is 12% higher than the advertised speed. During this speed test ISP offers a download speed of 100 Mbps. Hence the true internet speed is 112 Mbps.

As concluded earlier, only SpeedOf.me measures your true internet speed.

### The advertised internet speed

With an advertised internet speed of 100 Mbps and the knowledge that speed tests like Ookla and Cloudflare measures 90% of the true internet speed, the "correct" speed to measure is 90% of 112 Mbps or more concrete 100.8 Mbps.

In this test, we examine which speed test is the most accurate, assuming 100.8 Mbps is the correct value to measure.

## Method of measurement

For this test the download speed is measured five times per speed test.

## Speed tests to test

For this test only the mainstream speed tests mentioned at Which speed tests to test are tested.

## The measurements

- Cloudflare 101, 101, 100, 100, 100 Mbps, median: 100 Mbps, standard deviation: 0.5 Mbps, average 100.4 Mbps, precision 0.48%
- Fireprobe® 101.80, 101.58, 101.73, 102.05, 102.53 Mbps, median: 101.8 Mbps, standard deviation: 0.4 Mbps, average 101.94 Mbps, precision 0.28%
- Google Fiber 102, 102, 101, 101, 101 Mbps, median 101 Mbps, standard deviation: 0.5 Mbps, average 101.4 Mbps, precision 0.47%
- M-Lab 100.34, 100.82, 100.83, 101.51, 100.71 Mbps, median 100.82 Mbps, standard deviation: 0.4 Mbps, average 100.84 Mbps, precision 0.26%
- Meter.net 100.8, 100.5, 100.2, 100.6, 99.80 Mbps, median 100.5 Mbps, standard deviation: 0.4 Mbps, average 100.38 Mbps, precision 0.30%
- Ookla Speedtest 102.09, 101.18, 101.56, 102.81, 101.68 Mbps, median 101.58 Mbps, standard deviation: 0.6 Mbps, average 101.86 Mbps, precision 0.46%
- SpeedSmart 102.8, 103.1, 102.4, 102.5, 102.5 Mbps, median 102.5 Mbps, standard deviation: 0.3 Mbps, average 102.66 Mbps, precision 0.23%
- TestMy.net 100.6, 101.6, 100.6, 101.5, 101.3 Mbps, median 101.3 Mbps, standard deviation: 0.5 Mbps, average 101.12Mbps, precision 0.41%

## Conclusions

Based on the measurements above it can be concluded that:

- Based on the average of the measurements M-Lab is most accurate with a bias of +0.04 Mbps and a precision of 0.26%
- Also based on the average of the measurements Fireprobe®, Ookla Speedtest and SpeedSmart have the all biases greater than 1 Mbps

### The top 5 of accurate speed tests

Based on the absolute bias based on the average of the measurements this is the top 5 of most accurate speed tests (when the advertised internet speed is 100 Mbps):