Desmos for the SAT · Start here
Desmos Basics: The Interface
Type an equation, read the graph, and the four buttons that matter.
Nova again. Good news: you do not need to learn all of Desmos. Just five things. Once these feel automatic, every technique in this series is a two-minute read.
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Five buttons. That is the whole interface you need for the SAT. Play with each embedded calculator below as you read, do not just skim it.
Type an equation, it graphs instantly
The list on the left is where you type. Enter something like y = 2x + 3 on a line and Desmos draws it the moment you finish. Each new line is a new graph, so you can stack several at once.
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Go ahead, mess with it. Change the 2 to a 5 and watch the line snap steeper, or add a second line like y=-x+1 on the next row. It redraws the instant you type, that live feedback is the whole point.
Already loaded with y=2x+3. Add a second line, like y=-x+1, and watch both draw at once.
Desmos marks the answer for you
Here is the move that makes Desmos worth it: when two graphs cross, or a curve hits an axis or turns around, Desmos drops a little grey dot right on that point. Click the grey dot and it shows you the exact coordinates. You are not eyeballing the grid, you are reading the number Desmos hands you.
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Grey dots are gold. Crossings, intercepts, the top or bottom of a curve, Desmos marks them all. Click one and the exact answer pops up.
Two lines are loaded. Find the grey dot where they cross, click it, and read the coordinates. That point, (2, 7), is the solution to the system.
Zoom and pan to see the answer
If the point you need is off the screen, scroll to zoom or use the plus and minus buttons in the top right, and drag the graph to move around. This matters when a vertex or an intercept sits outside the default window.
Turn decimals into fractions
Desmos often shows a value as a decimal like 1.333, but SAT choices are usually fractions. Click the round fraction-converter button next to the value and it flips to 4/3. This one button saves you on a lot of answer choices.
Make a slider for an unknown
Type an equation with a letter that is not x or y, like y = ax + 1, and Desmos offers to add a slider for a. Drag the slider and the graph updates live, which is how you test an unknown constant.
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Grab the a slider and drag it back and forth. Watch the line pivot in real time as the value changes. That is exactly how you hunt for the value of an unknown constant on a real question.
The slider for a is already here. Drag it and watch the line tilt, that live update is how you test an unknown constant.
Use a list for data
For statistics and regressions, type your numbers as a list in square brackets, like L_1 = [3, 5, 8, 12]. Then you can run a function on the whole list at once, which is the heart of the data techniques later on.
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See the mean pop out as 9.2? Now you try the other two on the next line: type median(L1) for the middle value, or stdev(L1) for the standard deviation. Same list, one function each.
The list L_1 is loaded, with mean(L_1) already computing its average of 9.2. One function, the whole list at once.
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That is the interface. Next you put it together and solve your first real question by graphing.
Now put it on a real SAT question
SAT Prep Quest drills let you practice these Desmos basics on real SAT questions, adapting to what you miss so nothing feels new on test day.
Practice freeSAT is a registered trademark of the College Board, which was not involved in producing, and does not endorse, this product. Score estimates are Learner Labs projections, not official College Board scores.