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Kristin Fracchia

Math Formulas on the ACT [PDF]

Unlike the SAT, the ACT does not provide you with any formulas to use on the test. So you need to be able to recall them. Below you will find lists of “Must Know” formulas, “Good to Know” formulas, and “Bonus” formulas to commit to memory for the ACT!

Important ACT Math Formulas to Know (PDF)

Sometimes it’s easier to memorize formulas by studying a little bit every day. To make this easier, we created a downloadable, printable Magoosh ACT Math Formulas PDF.

Click here to download the free Math Formulas on the ACT PDF!

math formulas on the ACT 

Must Know ACT Math Formulas:

Though the ACT tests different concepts on each exam, there are popular topics that come up again and again. This list contains the best ACT math formulas to know, in addition to some extras (for all you over-achievers out there). Bonus: the math formulas on the ACT also appear in your high school math classes. So, you’re really studying for two things at once. Nice.


S/T (Average = Sum/Number of things)


Slope intercept form:
y = mx + b (where m is the slope and b is the y-intercept)

Slope Formula


Perimeter of a rectangle:
2l + 2w (where l is the length and w is the width)

Area of a rectangle:
lw (length x width)

Volume of a box:
lwh (length x width x height)

Surface area of a rectangular solid:
2lw + 2wh + 2lh

Diagonal in a rectangular solid:
Apply the Pythagorean theorem twice or
Diagonal in a rectangle formula


Area of a triangle:
1/2bh (1/2 base x height)

Circles and Spheres:

Area of a circle:
Area of a circle

Circumference of a circle:
Circumference of a circle

Volume of a sphere:
Volume of a sphere


Volume of a cylinder:
Volume of a cylinder

Pythagorean Theorem:

Pythagorean Theorem


sin x = opposite/hypotenuse
cos x = adjacent/hypotenuse
tan x = opposite/adjacent


You should also know your quadrants and where sine, cosine, and tangent are positive or negative:

Trig quadrants


Number of desired outcomes / number of total outcomes

Factorials (e.g. 8!):
To find the factorial of any integer, multiply it by every positive integer below it, e.g.:
8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

Formulas that are Good to Know

Equation of a circle:
Equation of a circle

Volume of a cone:
Volume of a cone

Volume of a pyramid:
Volume of a pyramid

Arithmetic sequences:
Screen Shot 2015-03-19 at 3.48.36 PM

Geometric sequences:
Screen Shot 2015-03-19 at 3.50.08 PM


Screen Shot 2015-03-19 at 3.53.34 PM

Change of base rule:
Screen Shot 2015-03-19 at 3.53.40 PM


Area of a trapezoid:
Screen Shot 2015-03-19 at 3.55.47 PM
(Add the bases, divide by two, then multiply by the height.)

30-60-90 Triangle Ratio:

act math formula 30-60-90 triangle magoosh


45-45-90 Triangle Ratio:

Screen Shot 2015-03-19 at 3.57.17 PM


Exponential Growth Formula:

Exponential growth formula

Where P = principal (starting value), r = rate of growth, n = number of months, t = time in years, and A = new amount.

Bonus Things to Know

Quadratic Equation:

Quadratic Equation

Often, you will be better off applying a strategy such as backsolving to solve a complicated algebra problem, but if you are comfortable with the quadratic equation, keep it in the back of your mind.





Let us know if you have any questions about these ACT formulas. 🙂
Image Credit: hotmath.com and getmathhelp.jimdo.com


About Kristin Fracchia

Kristin makes sure Magoosh's blogs are chock-full of awesome, free resources for students preparing for standardized tests. With a PhD from UC Irvine and degrees in Education and English, she’s been working in education since 2004 and has helped students prepare for standardized tests, as well as college and graduate school admissions, since 2007. She enjoys the agonizing bliss of marathon running, backpacking, hot yoga, and esoteric knowledge.

2 Responses to “Math Formulas on the ACT [PDF]”

  1. Jáksó Éva says:

    Is there any more formula which is needed for the ACT?

    • Magoosh Test Prep Expert Magoosh Test Prep Expert says:

      Hi there 🙂 We’ve done our best to compile most, if not all, of the formulas you’ll want to be familiar with on test day. While we can’t guarantee that the list is exhaustive, if you know how to apply the formulas we listed, you should be well on your way to ACT Math success 😀

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