Graphing calculator: plot functions, equations, polar and parametric curves and 3D surfaces (free)

What it does

This is a graphing calculator that runs in your browser. Type one or more curves and they are drawn together, each in its own colour-blind safe colour. It understands four kinds of curve, worked out from the way you type them:

• y = f(x), a function of x, such as y = x^3 - 2x - 1 or y = e^x.
• An equation in x and y, such as x^2 + y^2 = 16 or x^3 + y^3 = 6x y. These implicit curves are traced with the marching squares method on a fine grid, and each point is placed accurately by bisection.
• Polar curves r = f(θ), such as r = 4cos(3θ). Type theta if your keyboard has no θ.
• Parametric curves (x(t), y(t)), such as (4sin(3t), 3sin(2t)).

Any other single letter, such as a, b or k, becomes a slider, so you can watch the graph change. e is Euler’s number and pi is π. Functions include sin, cos, tan, their inverses (asin, acos, atan), sinh, cosh, tanh, exp, ln, log (base 10), sqrt, abs, cbrt, min, max and atan2. Angles are in radians.

The 3D surface tab draws z = f(x, y) as a shaded wireframe that you can turn and tilt by dragging.

How to use it

1. Type a curve in the first box. Press Add a curve for more (up to 8). The line under each box says what kind of curve it read, or what is wrong.
2. Drag the graph to move around. Pinch, scroll the mouse wheel or press + and − to zoom. Reset view goes back to the start.
3. Tap or click a curve to trace it: the point and its coordinates appear. For y = f(x) curves the value is worked out exactly at that x.
4. Key points in the window lists, for every y = f(x) curve, its roots, local maxima and minima and where it crosses the y axis, and where it crosses the other curves. Type a number in Value at x to read every curve there.
5. Download the graph as PNG (twice the screen size), SVG (vector, for Inkscape, Illustrator or a report) or CSV (every plotted point).

Settings

• Equal scale keeps one unit the same length on both axes, so circles look round. It turns off if you type a window that stretches one axis.
• Window sets the exact x and y range.
• Ranges for t and θ set how far parametric and polar curves run. The default is 0 to 2π.
• In 3D, Grid sets how many lines the surface has, and Colour by height shades it from light (low) to dark (high).

Worked example

The example draws the cubic y = x³ − 2x − 1 and the circle x² + y² = 16 for x from −6 to 6. Key points lists the roots −1, −0.618034 and 1.61803 (the last two are (1 ± √5)/2), a local maximum at (−0.816497, 0.0886621), a local minimum at (0.816497, −2.08866), the y-intercept (0, −1), and the two places the cubic meets the circle: (−1.84025, −3.55155) and (2.0428, 3.43904). Typing 2 in Value at x gives y = 3 on the cubic and y = −3.4641, 3.4641 (±√12) on the circle.

How exact is it?

Roots and crossings are found by bisection to full double precision, so they are correct to about 15 digits; the page shows 6. Turning points use golden-section search and are good to about 8 digits in x. The checks behind this page compare it with Python’s numpy and scipy.

What it does not do

It does not do algebra (no symbolic derivatives or simplification), inequalities or shading, or regression on your data (use the calibration curve tool for fits, or the plot maker for data). Key points are found only for y = f(x) curves and only inside the window: zoom out to find more. An equation that touches zero without changing sign, such as (x² + y² − 4)² = 0, is not drawn; write x² + y² = 4 instead.

Frequently asked questions

Why is there a gap in tan x? The graph breaks where the curve jumps to infinity (an asymptote) or where it is not defined, instead of joining the two sides with a false vertical line.

Is anything sent anywhere? No. Every calculation runs in your browser, and the page works offline once it has loaded.

Can I use degrees? Angles are radians. To use degrees, multiply by pi/180, as in sin(x*pi/180).

Last updated 2026-11-09.