What you get
The calculator in Bluebook is a full graphing calculator, not a four function one. You can type equations and see them plotted, enter a system and click the intersection point to read its coordinates, define a function and evaluate it at a value, build a table of values, and add a slider for an unknown constant.
It is available on every one of the 44 Math questions across both modules. The old split between a calculator module and a no calculator module ended with the paper test.
It is not available during Reading and Writing, and neither is any other calculator.
The graphs of the two linear equations in a system are shown as lines ℓ and k in the xy-plane. What is the solution (x, y) to the system?
The four moves worth practicing
Intersections. Type both equations of a system and click where the curves cross. Desmos labels the coordinates. This replaces substitution and elimination on most system questions and removes the sign errors that come with them. It works for nonlinear systems too, where the algebra gets genuinely unpleasant.
Roots and vertex. Plot a quadratic and Desmos marks the x intercepts and the turning point when you click them. That covers a lot of Advanced Math without the quadratic formula, which is not on the reference sheet anyway.
Sliders. If a question asks for the value of a constant that makes something true, type the equation with a letter in it and Desmos offers to add a slider. Drag it and watch the graph. This turns an abstract question into something you can see.
Tables. Type a function and Desmos will show a table of values, which is useful when a question gives you data points and asks which function fits, or when you need to check a value quickly.
When not to reach for it
When the question is about structure rather than numbers. Which expression is equivalent to another, what a coefficient means in context, how many solutions an equation has: these are faster to reason through than to type. Reaching for Desmos by reflex on those questions costs time you need elsewhere.
When the algebra is two quick lines. Typing a complicated expression correctly takes real seconds, and a typo produces a confident wrong answer with no warning. The common failure is spending 40 seconds entering a problem that would have taken 15 on paper.
The decision rule: read the question, decide whether the path is algebraic or visual, then act. Deciding first is what separates using Desmos well from using it as a crutch.
Practice in Bluebook, not just on the website
The Desmos panel inside Bluebook is smaller than the full website and it sits over part of the question. Learning where it opens, how to resize it, and how the keyboard entry behaves is worth doing before test day rather than during Module 1.
The syntax quirks matter too. Squaring with the caret, entering fractions so the denominator does not swallow the next term, and using the correct variable names are all things that go wrong under time pressure if you have only used it casually.
Every official Bluebook practice test includes the same calculator, so you get this practice for free with the tests you should be taking anyway.
What it does not replace
Scratch paper. The test center provides it, and writing out a system, sketching a triangle, or listing what you know is faster than holding it in your head. Do not try to work entirely on screen.
Knowing the formulas. The reference sheet is geometry only, so slope, the quadratic formula, exponent rules, percent change, and the equation of a circle are all on you. Desmos partly substitutes, but the substitution is slower than knowing the formula on questions where the algebra is quick.
Grid-in rules. About a quarter of the 44 Math questions are student produced response, and Desmos will happily give you a correct value that you then enter in a format the box rejects. The entry rules are a separate thing to learn.