This is a great tool for visually checking your intended font scales.
Although it is best suited to web designers and developers, I find it useful when tidying up websites or experimenting with the impact of typography upon conversion. It's also great for using to quickly mock up landing pages or one-off campaigns.
Creator Jeremy Church produced the site after using the Modular Scale calculator by Tim Brownbecause he found it difficult to select the typography scales for his websites without a visual reference. Type Scale is intended to bridge that gap.