Graphing calculator for Digital SAT maths practice
Type an equation the way it is printed and it is graphed. Tap a line or a curve and its intercepts, turning point and crossing points are marked with their coordinates. Free, with no account, and what you type stays on your device.
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What to type
Type maths the way it is written on paper. Multiplication needs no sign, so 2x is two times x, and 1/2x is a half times x. The test’s calculator builds a fraction, a power or a subscript as you type and keeps the cursor inside it until you press the right-arrow key, so there 1/2x is one over 2x, and a half times x is typed 1/2 → x. The moves mark every → a row needs.
| Type | What happens |
|---|---|
y = 2x + 1 | Graphs a line. A bare 2x + 1 does the same. |
5x + 9 = 3x + 25 | Draws a vertical line at the value of x that makes both sides equal. |
4x + 3y = 41 | Graphs an equation in both variables as it is written. |
x^2 + y^2 = 25 | Graphs a circle. Brackets move its centre: (x - 2)^2 + (y + 1)^2 = 25. |
f(x) = x^2 - 4 | Defines a function. A later row can then ask for f(3). |
a = 3 | Makes a slider for a, usable in any other row. |
y < 2x + 1 | Shades one side of the line. A second inequality darkens the overlap. |
mean([3, 5, 8, 12]) | Prints a value. median, total, stdev and the rest work the same way. |
y_1 ~ m x_1 + b | Fits a line to a table whose columns are x_1 and y_1, and prints m and b. |
(x + 5)/3 = 2x - 15 | Reads here as it is written. In the test-day calculator the 3 starts a denominator that keeps everything typed after it, so press → (the right-arrow key) after the 3. |
It is not the calculator on the test, and that matters
The Digital SAT has the Desmos graphing calculator built in, available for the whole Math section. This is our own calculator, written to do what the test’s does: the same notation, the same tap for a curve’s points, sliders, tables and fitted lines. One thing differs in how a row is typed: there, a fraction, a power or a subscript keeps the cursor until you press the right-arrow key.
Built to match is not the same as identical, so practise on the real one too. The College Board version of the Desmos calculator is free and needs no account. Anything you learn to do here, do there once before test day.
We keep a list of the behaviours students rely on. Each one is typed into the College Board version of Desmos and what it shows is recorded, with who checked it and the date. Ours is computed from this calculator whenever the page is built.
What our calculator matches, and what it does not
11 of 12 checked behaviours match the College Board version of Desmos. Each Desmos answer was typed into it and recorded, with who checked it and the date; ours is computed from this calculator whenever the page is built.
| Behaviour | Ours | Desmos | Checked |
|---|---|---|---|
| stdev() of a list is the sample standard deviation | 1.291 | 1.291 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| stdevp() of a list is the population standard deviation | 1.118 | 1.118 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| y = 1/2x reads as a half times xIn the test-day calculator, typing 1/2x gives one over 2x. Here it is a half times x, the way a slope is printed. To get a half times x there, press the right-arrow key after the 2. | 2 | 0.125differs | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| An exponential regression through (0, 3), (1, 6), (2, 12), (3, 24) finds the growth factor | 2 | 2 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| [1...10] is the list of the whole numbers 1 to 10 | 5.5 | 5.5 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| A function defined on one line can be evaluated on the next | 10 | 10 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| A restriction {0 < x < 5} keeps the graph where it holds | 4 | 4 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| …and draws nothing where it does not | nothing drawn | nothing drawn | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| Two inequalities shade their overlap: (0, 0.5) lies in both y < x + 1 and y > −x | yes | yes | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| log() is base 10 | 2 | 2 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| ln() is the natural logarithm | 2 | 2 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
| The angle unit a new calculator starts in | -0.988 | -0.988 | Claude (an AI assistant), typing in a browser, 2026-10-14 |
Your working stays with you
What you type is kept in this page’s address, after the # sign. Browsers do not send that part of an address to a server, so nothing you type reaches us. It also means a reload does not lose your work, the Back button undoes a cleared calculator, and Copy link gives you an address that opens the same graph on another device.
Methods that use it
A calculator is only as fast as knowing what to type and where to look. Each of these is one method, on a worked question, with five more to practise on.
Type the equation as written
Solve a linear equation by typing it into the graphing calculator
Two graphs, one crossing
Solve a system of equations by graphing both lines
Tap the turning point
Find the maximum or minimum of a quadratic by graphing it
Turn the mean back into a total
Solve mean problems by turning the mean back into a total
Put a number in, or graph the choices
Find the equivalent expression by putting a number in
Let the table find the constants
Fit a linear, quadratic or exponential model to a table of values
Common questions
- Is this the calculator used on the Digital SAT?
- No. The Digital SAT has the Desmos graphing calculator built into the test, and this is our own calculator, built to work the same way for what the test asks of it. Practise on the official one as well: the College Board version is free on the Desmos website and needs no account.
- Is the calculator free?
- Yes. There is no account, no trial and nothing to download. It is the same calculator that opens beside the Math questions in a Preptics practice test.
- Does it save or send what I type?
- It keeps what you type in the part of the page's address after the # sign. A browser does not send that part to any server, so what you type stays on your device. Reloading the page keeps it, and Copy link gives you an address that opens the same calculator.
- Can I use it on a phone?
- Yes. On a narrow screen the list of expressions sits above the graph, and the calculator has its own keys for the symbols a phone keyboard hides. Pinch to zoom and drag to move the graph.
- Does it work in degrees?
- Yes. The Radians and Degrees switch is at the top of the calculator. It starts in radians.
The interactive figures for single topics: every tool. How the calculator fits into a practice test: the exam it sits in.
SAT® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, this site. All practice questions and reading passages are original works created by Preptics and are not actual SAT® questions. Desmos is a trademark of Desmos Studio, which is not affiliated with Preptics and does not endorse this calculator.