The digital SAT puts a full Desmos graphing calculator inside Bluebook, the app you take the test on, and it is available on every math question. Tom tells students who haven’t trained with it that getting very good at Desmos is the most important thing they can do for their math score, which is why the Deep Test Prep library opens its math lessons with Desmos. Many questions go faster in Desmos, and many more become harder to get wrong, because the calculator does the arithmetic and draws the picture for you.
Desmos also has limits. Many SAT questions test whether you understand a situation, such as which number in a story is the starting amount and which is the rate, and no graph can supply that understanding. The skill this guide teaches is choosing: Desmos for the questions it answers faster or more safely, and your own reading and algebra for the rest.
Students usually learn that choice in three stages, and the sections below follow them. They start with what Desmos does well and how to type into it, then turn to the habit of leaning on it too much, the practice of solving both ways that breaks the habit, and the right time to use it for checking.
Learning Desmos, from the Controls to Knowing When to Use It
The first stage is learning the calculator itself: typing expressions, reading graphs, and knowing the features that answer a question in a click. The second stage arrives once typing is easy, when many students start typing every equation they see before they’ve read the question. The third stage is judgment: within seconds of reading a question, you know whether it belongs in Desmos. Each stage has its own typical mistake, so the practice that helps you most depends on which stage you’re in.
Where you are with Desmos, and what to work on next
What it looks like
- You hunt for keys and aren't sure how to type an exponent or a fraction.
- You haven't learned that clicking a graph shows its intercepts and crossing points.
- You do long calculations by hand because typing them feels slower.
What to work on
Practice entering expressions and reading graphs until the calculator feels as familiar as a pencil.
When typing is easy, watch for the opposite problem: typing too soon.
Where Desmos Saves Time and Mistakes
The mistake
Solving graph questions and long calculations by hand when Desmos would do them faster and more safely.
The fix
Learn the kinds of questions Desmos answers in a click or two, and practice typing until the calculator feels as quick as a pencil.
Desmos draws any equation you type and marks its important points. Click a graph, and gray points appear where it crosses the axes, where it turns, and where it meets another graph, each labeled with its coordinates. When a question asks for one of those points, Desmos can answer it without a line of algebra. The rows below show the kinds of questions that work this way, with the point to click drawn in blue.
A point two graphs share
A system of equations asks for the point on both graphs. Graph each equation and click where they cross.
The solutions of an equation
Graph each side of the equation as its own curve. The x-values where they cross are the solutions.
A highest or lowest value
Click the top or bottom of a parabola. The y-value is the greatest or least amount, and the x-value is where it happens.
Zeros and intercepts
Click where a graph meets the x-axis to see its zeros, and where it meets the y-axis to see its starting value.
Arithmetic with awkward numbers
Percentages, decimals, and long expressions are quicker and safer as a single typed line than as work on scratch paper.
Desmos helps even when it can’t give the answer directly. A graph shows whether a function grows or shrinks, where it turns, and how many times it meets a line, and that picture often points to the method to try next. Desmos is also an ordinary calculator, and typing a long expression as one line avoids the arithmetic slips that happen on scratch paper.
Entering Exactly What the Question Says
The mistake
Typing an expression the way it looks and trusting whatever number comes back.
The fix
Add parentheses wherever the printed math groups things, and read the typed line against the question before you trust the result.
Desmos computes exactly what you type, and an expression typed the way it looks can be grouped differently from the printed one. Squaring a negative number, putting a sum on top of a fraction, and raising a number to an exponent with two terms are three places where that happens. An accurate calculator still gives a wrong answer to a mistyped expression, so parentheses are part of the math.
What Desmos computes when you type what you see
Printed in the question
Typed the way it looks
- -
- 3
- ^
- 2
What number does Desmos show for the typed line?
The same care makes Desmos a good way to check your own arithmetic. If you tend to make sign errors, type a line of your work into Desmos and compare the results, with parentheses in the typed line wherever the printed math has them. When Desmos gives a number that surprises you, read the typed line against the question before you accept it.
Reading the Question Before Typing Into Desmos
The mistake
Typing every equation into Desmos before you know what the question asks.
The fix
Read the whole question first, decide what it asks for, and only then choose a tool.
Once typing is easy, a new habit tends to appear: a student sees an equation and starts typing it before finishing the question. At that point Desmos has become a crutch that does the thinking the question was written to test, and the student is stuck whenever the calculator can’t help. The College Board says the Math section includes some questions where it’s better not to use a calculator, and in Tom’s experience, most SAT math questions are ones Desmos can’t answer for you, or can help with only indirectly.
Word problems that ask for a model are the clearest case. The question describes a situation, and the answer choices are equations. Every choice graphs as a perfectly good line or curve, so graphing them can’t show which one fits. Choosing the right model takes understanding the situation: which quantity is the starting value, which is the rate of change, and whether the change is linear or not.
Which part of this story is the rate of change?
Pick one of the underlined words.
The sorter below mixes all three kinds of questions. For each one, decide in a few seconds whether Desmos, a few lines by hand, or careful reading gets you to the answer, and then read the reason.
Desmos, by hand, or read and reason?
Question 1 of 6
What is the -coordinate of the point where and intersect?
Questions to ask yourself
- Does the question ask for a number, a point, an equation, or what something means?
- Is the answer a point Desmos can mark, such as a crossing, a highest point, or a zero?
- Do I need to know what each number means before any equation can help?
- Would a few lines of algebra be quicker than typing and clicking?
Solving Both by Hand and in Desmos
The mistake
Guessing which method is faster instead of finding out.
The fix
During practice, solve each question both with Desmos and by hand whenever both are possible, and write down which one worked better.
The way out of the second stage is to do problems both ways. When you practice, solve each question with Desmos and with algebra whenever both are possible, and keep track of which one was quicker and which one you trusted more. The explanations in a lesson can say which method they would choose, and you develop your own sense of it only by trying both. Choose a method below before you watch both solutions.
The same problem by hand and in Desmos
Which method would you reach for?
Keep a short log as you practice. For each question, write down what kind of question it was, which method worked better, and what in the question could have told you so. After a few weeks, the log becomes a list of question types you recognize on sight.
Kind of questionA system of two linear equations
Better methodDesmos
What in the question tells youThe question gives two equations and asks for the point, or one coordinate of the point, that makes both true.
Kind of questionAn equation that models a situation
Better methodRead and reason
What in the question tells youThe answer choices are equations, and the question asks which one represents the story.
Kind of questionA linear equation with whole numbers
Better methodBy hand
What in the question tells youThere is one variable, and each step undoes one operation, so two or three lines finish it.
Kind of questionA greatest or least value
Better methodDesmos
What in the question tells youThe question asks for a maximum, a minimum, or the highest or lowest amount of something a function describes.
Solving both ways teaches more than method choice. Working the same kinds of questions again and again shows you the patterns the SAT repeats, and timing both methods tells you how long each kind of question takes you. Practice done this way builds your judgment about Desmos and your knowledge of the test at the same time.
Checking Uncertain Answers With Spare Time
The mistake
Rechecking answers while easier questions are still unanswered, or rechecking by rereading the same work.
The fix
Once every question within reach has an answer, use the time left to solve your least certain ones a different way.
If you finish a module early, go back to the questions you were least sure about and solve each one a slightly different way. When Desmos and your algebra agree, move on. When they disagree, one of them has a mistake worth finding, often a sign error or a misplaced parenthesis. Checking is for spare time, after every question within reach has an answer. Questions in each module run from easiest to hardest, and an easy question left blank while you double-checked a hard one is a question you could have gotten right.
Which questions get a second look
- 1
- 2
- 3
- 4
- 5
- 6 (unsure)
- 7
- 8
- 9
- 10
- 11
- 12
- 13 (unsure)
- 14
- 15
- 16
- 17
- 18
- 19 (unsure)
- 20
- 21
- 22
Answer every question within reach, easier ones first. When you're unsure of an answer, choose your best one and mark the question for review.
Bluebook lets you mark any question for review, and its question list shows which ones you marked, so the uncertain questions are easy to find when the time comes.
What to Practice Once Desmos Is Easy
In the third stage, about five or ten seconds of reading usually tells you whether a question belongs in Desmos. You use the calculator efficiently, you use it to check the calculations where you tend to slip, and it often leaves you with extra time at the end of a module. Getting here takes a good amount of practice, and the time is well spent.
At this point, Desmos is rarely what limits your score. What remains is the math: the question patterns the test uses, the equations that go with them, and the content behind them. Once Desmos is fluent, spend most of your practice on the math content and question patterns you haven’t mastered yet.
Sources
Facts on this page were checked on September 26, 2026. Test features can change, so confirm details with the College Board.
- 01College BoardCalculator PolicyBluebook's embedded Desmos calculator, the handheld calculators allowed, and the note that some math questions are better done without a calculator.
- 02College BoardSAT Test Directions in BluebookThe Math directions: a calculator is permitted for all questions, and each of the two modules has 22 questions.
- 03College BoardMath Section OverviewThe Math section's four content domains, and the order of questions in each module, from easiest to hardest.
- 04Desmos Help CenterGetting Started: Desmos Graphing CalculatorThe gray points of interest Desmos marks on a graph, such as intercepts and intersections, and how to reveal their coordinates.
- 05Desmos Help CenterPractice With Testing CalculatorsWhere to practice with the version of Desmos configured for the SAT, which turns off some features of the full calculator.