Desmos

Desmos is the world's most widely deployed free graphing calculator — used by hundreds of millions of students, integrated into state standardized tests (including SAT), and built into curricula across the United States and internationally.

## Real-Time Interactive Graphing

Type any equation — linear, quadratic, trigonometric, parametric, polar — and Desmos renders it as an interactive graph instantly. Graphs are touch-friendly: zoom, pan, tap to see coordinates. Multiple equations overlay on the same axes. Change a value and the graph updates immediately.

The real-time interactivity makes Desmos dramatically better than static textbook graphs for understanding math: you can see what happens to y = ax² as you drag a slider changing a from -3 to 3.

## Sliders and Animations

Desmos sliders are its most powerful teaching feature. Define a parameter (like "a" in y = a·sin(x + b)) and Desmos adds a draggable slider. You see function behavior change continuously as you adjust parameters — making abstract function transformations concrete and intuitive.

Sliders can be animated: Desmos will cycle through values automatically, creating animations of rotating functions, evolving curves, or dynamic data.

## Regressions and Statistics

Paste a table of data points and Desmos fits a regression curve: linear, quadratic, exponential, logarithmic, or custom. It displays the equation of best fit and R² value. This is genuinely useful for data analysis in courses from pre-algebra through AP Statistics.

## Geometry Tool

Desmos Geometry is a separate tool for Euclidean geometry constructions: points, lines, circles, polygons, angle measures, and geometric transformations. Build constructions interactively and explore geometric relationships.

## Desmos Classroom Activities

Desmos Classroom (formerly teacher.desmos.com) is a platform for building interactive math lessons: create activity sequences where students move sliders, build graphs, and respond to prompts. Teachers can see student responses in real time. Over 100,000 teacher-created activities are available in the public library.

## SAT and Standardized Tests

Desmos Graphing Calculator is built into the College Board's digital SAT. Students should be familiar with Desmos if they're taking the digital SAT.

## Pricing

Desmos Graphing Calculator, Geometry, and Scientific Calculator are completely free, forever. Desmos Classroom for teachers is free for classroom use. No ads, no premium tier — Amplify Education acquired Desmos and funds it as a free public resource.