Using the tools
Inputs and buttons can be reached with a keyboard. Calculator results have text labels and an announcement region. The visual rate slider has an equivalent written equation, so colour is not the only way to understand the result.
Reading without interaction
Each calculator post includes a formula and a worked example. JavaScript is needed for live calculation and invoice rows; the educational content remains readable without it. Use browser zoom to enlarge the interface.
If something is difficult
Use the written examples to check your inputs, or try a different browser with JavaScript enabled. Site owners should publish their own support contact and review accessibility as plugins and content change.