Many developers don't think about calculators until they need one. Whether it's debugging formulas, checking statistics, verifying algorithm outputs, or working through engineering calculations, having a reliable calculator nearby can save time.
As someone who frequently works with numbers, I've found that browser-based graphing calculators are especially useful because they don't require any installation and are accessible from any device.
A few situations where I use an online graphing calculator:
Testing mathematical formulas
Verifying calculations during development
