The complete guide to Desmos on the digital SAT
Updated
The digital SAT gives you the Desmos graphing calculator on every math question, built right into the Bluebook testing app. Used well, it turns many of the test's hardest questions into a minute of typing and clicking. Used badly, it's a distraction.
This guide covers the nine Desmos moves that solve most SAT math questions, with a short worked example of each and links to step-by-step guides for the biggest ones. Then it covers when not to use Desmos, and how to get fast before test day.
Desmos on the digital SAT: the basics
- It's available on every math question, in both modules. Open it from the calculator button at the top of the screen.
- It's the Desmos graphing calculator, with graphing, tables, sliders, regressions, and statistics functions. If you've used Desmos in class, it will feel familiar.
- You can still bring your own calculator, as long as it's on the College Board's approved list. Many students use Desmos for graphing and their own for quick arithmetic, or Desmos for everything.
- Practice with it before test day. The full-length practice tests in Bluebook use the same calculator, so you'll know where everything is.
1. Graph both sides and find the intersection
For systems of equations, and for any equation that's awkward to solve by hand, graph each side and click where the graphs cross. The -coordinate is the solution. The full method is in how to solve systems of equations with Desmos.
An equation with a square root
Type and . They cross at one point, .
Solving by hand means squaring both sides, which produces a second answer, , that doesn't actually work. Desmos only shows the real crossing, so you never fall for it.
Answer:
2. Click the gray points: zeros, maximums, and minimums
Click any graph and Desmos marks its -intercepts and turning points. No factoring, no vertex formula. See how to find the vertex and zeros with Desmos.
A maximum value
Graph it and click the curve. The vertex is , so the maximum value is . (The maximum is the -value, not the -value.)
Answer:
3. Use a slider for an unknown constant
When a question asks "for what value of ", let Desmos turn into a slider and drag until the graph does what the question describes. See how to use Desmos sliders for value-of- questions.
Touch the x-axis once
Type and add a slider for . Drag until the vertex sits exactly on the -axis: at , the vertex is .
Answer:
4. Fit data with a regression
Given a table, enter it as lists and type a model with ~, and Desmos finds the equation. See how to use Desmos regression on the SAT.
Which linear function?
- A.
- B.
- C.
- D.
Type , , and . Desmos shows and .
Answer: A,
5. Define functions and evaluate them
Type a function once with its name, and Desmos evaluates it anywhere, including inside another function.
A composite function
Type , then , then . Desmos shows . (Inside out: , and .)
Answer:
6. Lists and statistics
Put a data set in square brackets, then use mean, median, and other statistics functions instead of adding by hand.
Mean vs. median
Type , then and . Desmos shows and .
The outlier, 45, pulls the mean up but barely moves the median. That's a favorite SAT idea.
Answer:
7. Plot the answer choices
When the choices are points, graph the question's equations or inequalities, then type each choice and see which one lands in the right place.
Which point is a solution?
- A.
- B.
- C.
- D.
Type both inequalities; Desmos shades each one. Then type the four points. Only sits inside both shaded regions. is the trap: it lands exactly on the dashed boundary of , and a dashed boundary isn't included.
Answer: C,
8. Graph equations exactly as written
Desmos graphs equations in any form. That's a big shortcut for circles, where the algebra means completing the square twice.
A circle's radius
Type the equation as written. The circle reaches from on the left to on the right (zoom in on the grid to check), so its diameter is and its radius is . Its center is halfway, at .
Answer:
9. Quick calculations
Desmos is a full scientific calculator too: percents, fractions, square roots, trig, and a distance function.
Discount, then tax
Type . Desmos shows .
Answer: $73.44
When not to use Desmos
Desmos is a tool, not a reflex. Skip it when:
- The algebra is one step. If , just divide.
- The question is about structure. "Which expression is equivalent to..." questions with letters for constants are often faster by reasoning, though sliders can check you.
- You'd spend longer setting it up. Long word problems sometimes need you to write the equation first. Write it, then graph it.
How to get fast before test day
- Learn the moves one at a time, with a few problems each, until you recognize which move a question calls for.
- Practice with the calculator beside the question, the way Bluebook shows it, not in a separate tab.
- Time yourself. The math modules give you about a minute and a half per question, so the goal is a setup you can do without thinking.
- Review your misses and ask which Desmos move would have solved each one.
Practice every move
Practice on real SAT-style problems
Intersect Prep puts the same Desmos calculator beside 306 SAT-style problems, with a step-by-step strategy for each one. Create a free account to try a full lesson with the calculator; a pass unlocks the rest.
Questions
- Is Desmos allowed on the digital SAT?
- Yes. A Desmos graphing calculator is built into the Bluebook app and available on every question in both math modules.
- Can I bring my own calculator to the digital SAT?
- Yes, if it's on the College Board's list of approved calculators. You can use it instead of, or alongside, the built-in Desmos calculator.
- Is Bluebook's Desmos the same as the Desmos website?
- It's the same Desmos graphing calculator, with graphing, tables, sliders, regression, and statistics. Bluebook's practice tests use it, so practice there to see it exactly as it appears on test day.
- Which Desmos tricks are most useful on the SAT?
- Graphing both sides to find an intersection, clicking gray points for zeros and vertices, sliders for unknown constants, and regression for tables. Together they cover a large share of SAT math questions.