One hundred point eight

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

  1. Introduction
  2. Method of measurement
  3. Speed tests to test
  4. The measurements
  5. Conclusions
 

Introduction

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

  1. the true internet speed
  2. 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.

Accuracy score

We have updated this page in 2025 with our standarized accuracy score (and the indication Mainstream).

This accuracy score allows us to easily objectively assess speed tests for accuracy.

 

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

  1. Cloudflare 101, 101, 100, 100, 100 Mbps, median: 100 Mbps, standard deviation: 0.5 Mbps, average 100.4 Mbps, precision 0.48%, accuracy score: 99 Mainstream
  2. 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%, accuracy score: 98 Mainstream
  3. Google Fiber 102, 102, 101, 101, 101 Mbps, median 101 Mbps, standard deviation: 0.5 Mbps, average 101.4 Mbps, precision 0.47%, accuracy score: 100 Mainstream
  4. 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%, accuracy score: 100 Mainstream
  5. 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%, accuracy score: 100 Mainstream
  6. 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%, accuracy score: 99 Mainstream
  7. 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%, accuracy score: 95 Mainstream
  8. 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%, accuracy score: 99 Mainstream
 

Conclusions

Based on the measurements above it can be concluded that:

  1. Three speed tests (Google Fiber, M-Lab and Meter.net) have an accuracy score of 100
  2. Of these three speed tests M-Lab and Meter.net have the lowest standard deviation
  3. 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%
  4. Also based on the average of the measurements Fireprobe®, Speedtest and SpeedSmart have the all biases greater than 1 Mbps
  5. The standard deviation varies from 0.3 Mbps to 0.6 Mbps