17 Important Math Formulas Students Should Know

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As any student knows, tough math problems are difficult enough without needing to remember the right formula. So, it’s important to have all the right tools in their back pocket! 

Remembering the step-by-step methodology required to solve complex math problems is demanding enough for students. The last thing they need is to try and recall a tricky formula on top of that! 

Whether your child needs to brush up to tackle their homework or needs to remember the essentials for a big test or quiz, these formulas are sure to come in handy. 

Important Math Formulas

Math can be a fun challenge or a students’ headache: these formulas will be useful no matter where your child falls on that spectrum. We’ve got you covered no matter what. 

Elementary & Middle School

Area of Rectangle: area = length x width

Kids will need to know this one in pre-algebra and later math classes. 

Perimeter of a rectangle: 2(l + b)

This will calculate the total of the outer lines of a rectangle. 

Area of a square: a² 

Square the length of both sides to find the area of a square. 

Perimeter of a square: 4 x a

Multiply the length of the side of the square by 4 to find the perimeter. 

Area of a circle: π x r²

Use this to find the total area of a circle. 

Circumference of a circle: 2π x  r

This formula calculates the length of the outside of a circle.

Find the Average: Sum of total numbers divided by the number of values. 

Useful in statistics and many more math word problems. 

Useful High School and SAT® Math Formulas  

These high school math formulas will come in handy in geometry, algebra, calculus and more. Plus, when SAT® season arrives, they will help teens succeed on the challenging math section.

(Looking for more SAT® math help? Check out 11 SAT® Apps for Daily Practice and How to Study for a Math Test.)

The Quadratic Formula: x = −b ± √b²-4ac/2a

Students will need this to solve quadratic equations in algebra II and beyond. As an added pneumonic bonus, it’s easier to remember this one to the tune of “Pop Goes the Weasel”. 

Probability: Number of favorable outcomes divided by the total number of favorable outcomes.

To determine the probability of an event, this equation will determine the odds of something happening. 

Distance formula: d=√(x₁ – x₂)² + (y₁ – y₂)²

This equation will calculate the distance between two points, which will be necessary in geometry and algebra.

Slope Formula: Slope = y₂ – y₁ /  x₂ – x₁

Use this to find the angle that joins two points on a graph. 

Slope Intercept Formula: y=mx+b

In algebra, this will find the slope intercept of a straight line. 

Area of Triangle: Area = (1/2) (base) (height)

Use this in geometry to find the total area of a triangle. 

Sine (SOH): Sine = opposite / hypotenuse

This equation calculates the unknown angles of a triangle. 

Cosine (CAH): Cosine = adjacent / hypotenuse

Use this equation to find the unknown angles of a triangle. 

Tangent (TOA): Tangent = opposite / adjacent

This equation also can be used to calculate the unknown angles of a triangle. 

The Pythagorean Theorem: a²+b²=c²

This is used to find the length of a hypotenuse in a right triangle. In any right triangle, the square of the length of the hypotenuse equals the sum of the squares of the lengths of the legs of the right triangle.

Got math problems? We’ve got math solutions! 

In addition to unparalleled math tutoring, iD Tech offers a wealth of math resources. Here’s a sneak peek:

With these helpful tips and tricks in hand, you’re ready to support your student with math homework, tests, quizzes, and the SAT®!

A photo of Virginia

Virginia started with iD Tech at the University of Denver in 2015 and has loved every minute since then! A former teacher by trade, she has a master's in education and loves working to embolden the next generation through STEM. Outside the office, you can usually find her reading a good book, struggling on a yoga mat, or exploring the Rocky Mountains. 

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