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!
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)
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
Area of a triangle:
1/2bh (1/2 base x height)
Circles and Spheres:
Area of a circle:
Circumference of a circle:
Volume of a sphere:
Volume of a cylinder:
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:
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:
Volume of a cone:
Volume of a pyramid:
Change of base rule:
Area of a trapezoid:
(Add the bases, divide by two, then multiply by the height.)
30-60-90 Triangle Ratio:
45-45-90 Triangle Ratio:
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
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