View it on the Chrome Web Store

This is a simple, lightweight Chrome extension that scans the webpage for instances of American odds (-130, +140, etc), and converts it to implied probability as a percentage. Click the extension icon to toggle it on and off.

For more on implied probability and gambling odds, check out my blog post.

Here are betting odds for a random NBA game:

Here's what appears after clicking on the extension:

Assuming the odds are "fair", the implied probability is the percentage chance that the bet is supposed to win. Because sportsbooks charge a fee or "vig" for placing bets, this number will appear slightly higher than the actual probability. This number is simpler way to look at sports betting: a "good bet" is one where you believe the percentage chance is higher than the implied probability.

Run the following command which will create a .zip including all the necessary files:

zip -r build.zip images/ background.js content_script.js manifest.json

And you're ready to upload your extension! To make your own extension you'll need to register as a Chrome Web Store Developer.