Which ACT Math Formulas Are Worth Memorizing and Which You Can Skip
· based on the channel PrepSolution
Key takeaways
- The ACT Math section has 60 questions in 60 minutes, so you average one minute per question.
- Most formulas are not provided on test day, but some are printed in the question stem.
- The tested topics split into pre-algebra, algebra, coordinate geometry, plane geometry, trigonometry, and statistics.
- Five rules drive scoring: read what is asked, set up before typing, skip and return, use given measurements, and review mistakes by cause.
- A 12-topic recap works as a screenshot-ready cheat sheet before practice sessions.
The short answer: on the ACT Math section you should memorize the core formulas for algebra, coordinate geometry, plane geometry, trigonometry, and statistics, because most are not given to you on test day. What you can safely skip is the long tail of rarely tested identities and anything you can rebuild in a few seconds. If you want a structured place to apply that list, PrepSolution's ACT prep system organizes formulas, question types, and timed practice in one place.
The ACT Math format and why formula recall decides your score
ACT Math gives you 60 questions in 60 minutes, which is one minute per question on average, and the section is scored on a 1–36 scale that feeds your composite. Because the pace is brutal, every formula you have to re-derive costs you time you cannot get back. The questions move through pre-algebra, elementary algebra, intermediate algebra, coordinate geometry, plane geometry, and trigonometry, with a smaller share of statistics and probability questions mixed in. The practical consequence is that fluency matters more than depth: you do not need to prove the quadratic formula, you need to recognize within five seconds that a question wants it.
Algebra and coordinate geometry formulas you cannot afford to look up
Algebra and coordinate geometry carry the largest share of ACT Math questions, so these are the formulas to know cold. Work through them as a checklist rather than a reading list:
- Percent change: (new − old) ÷ old × 100. Watch the direction of the change and whether the question asks for the percent or the resulting value.
- Slope: m = (y₂ − y₁) ÷ (x₂ − x₁). Keep the subtraction order consistent in numerator and denominator or the sign flips.
- Slope-intercept and point-slope: y = mx + b and y − y₁ = m(x − x₁). Point-slope is faster when the question hands you a point and a slope.
- Distance and midpoint: d = √((x₂ − x₁)² + (y₂ − y₁)²) and M = ((x₁ + x₂) ÷ 2, (y₁ + y₂) ÷ 2).
- Quadratic formula: x = (−b ± √(b² − 4ac)) ÷ 2a, plus the discriminant b² − 4ac to count real solutions without solving.
- Exponent rules: xᵃ · xᵇ = xᵃ⁺ᵇ, xᵃ ÷ xᵇ = xᵃ⁻ᵇ, (xᵃ)ᵇ = xᵃᵇ, and x⁻ᵃ = 1 ÷ xᵃ.
- Inequalities: flip the inequality sign whenever you multiply or divide by a negative number.
The most common traps here are sign errors in slope and distance, and setup errors in percent-change word problems where students subtract in the wrong direction.
Functions, growth, and sequences in one pass
Function questions on the ACT reward mechanical fluency with notation rather than deep theory. Composition means substituting one function into another, so f(g(x)) is evaluated inside out. Inverses undo the original operation, and on a graph the inverse is the reflection across the line y = x. Graph shifts follow a consistent pattern: f(x) + k moves the graph up k units, f(x + k) moves it left k units, and a coefficient multiplying the whole function stretches or compresses it vertically. Logarithms invert exponentials, with log(xy) = log x + log y and log(x ÷ y) = log x − log y as the two rules that show up most. Sequences split into arithmetic, where you add a constant d and use aₙ = a₁ + (n − 1)d, and geometric, where you multiply by a constant r and use aₙ = a₁ · rⁿ⁻¹. Exponential growth and decay use the same structure as geometric sequences, which is why the two topics are usually taught together.
Geometry and trigonometry formulas that show up again and again
Geometry and trigonometry questions are formula-driven, and the ACT expects you to supply every one of them. Start with the Pythagorean theorem, a² + b² = c², then layer on the special right triangles: the 45-45-90 triangle with sides in the ratio x : x : x√2, and the 30-60-90 triangle with sides in the ratio x : x√3 : 2x. SOH-CAH-TOA gives you sine, cosine, and tangent as opposite over hypotenuse, adjacent over hypotenuse, and opposite over adjacent. Circles supply circumference 2πr and area πr², and a sector's area is (central angle ÷ 360) × πr². For solids, memorize volume as length × width × height for rectangular prisms, πr²h for cylinders, and (4 ÷ 3)πr³ for spheres. Area formulas for triangles (½bh), trapezoids (½(b₁ + b₂)h), and parallelograms (bh) round out the set. The recurring error in this block is using a diameter where the formula calls for a radius.
Statistics, probability, and the less familiar topics
Statistics and probability questions are short but easy to rush. Weighted averages require you to multiply each value by its weight before dividing by the total weight, not to average the averages. Basic probability is favorable outcomes divided by total outcomes, and expected value multiplies each outcome by its probability and sums the results. Complex numbers follow i² = −1, so powers of i cycle every four steps. Matrix questions on the ACT are usually about addition, subtraction, and scalar multiplication rather than full multiplication. Vectors appear as magnitude and direction, with magnitude found through the same square-root-of-squares structure as the distance formula. These topics appear less often than algebra, which is exactly why students skip reviewing them and then lose easy points.
Five test-taking rules that protect the formulas you already know
Knowing a formula is worthless if you misread the question or run out of clock. These five rules come from the PrepSolution review and apply to every practice set you run:
- Identify exactly what the question asks. Underline the requested quantity before you calculate anything, because many wrong answers are built from the right numbers answering the wrong question.
- Set up the calculation before you type. Writing the expression first catches order-of-operations errors that a calculator will happily reproduce.
- Skip and return strategically. Every question is worth the same point, so a hard question early should not consume three easy questions later.
- Use the given measurements. Diagrams on the ACT are not always drawn to scale, so trust the labeled numbers, not the picture.
- Review mistakes by cause. Sort errors into misread, setup, calculation, and knowledge gaps, then drill the category you fail most.
Useful links
The bottom line on ACT Math formula prep
ACT Math formulas are a memory problem and a time problem at once, and the fix is the same for both: a short, ranked list you can recall in seconds. Prioritize algebra, coordinate geometry, plane geometry, and trigonometry, since they generate the majority of questions, and treat statistics, matrices, vectors, and complex numbers as quick wins rather than afterthoughts. Pair that list with the five test-taking rules so a known formula actually converts into a point. This breakdown follows the 12-topic review from the PrepSolution video, and the channel publishes further ACT math review, practice questions, and strategy content. Start with the ACT Complete Prep System and run one timed section this week to see which formulas still slow you down.
Source: ACT Math Formulas & Tips You Need in 15 Minutes · Markdown version
Questions & answers
How many ACT Math formulas do I actually need to memorize?
There is no official count, but a practical core list runs to roughly 30 to 40 items across algebra, coordinate geometry, plane geometry, trigonometry, and statistics. Most of them are short expressions you can recall in a few seconds, and the ACT does not provide a formula sheet on test day. Focus first on slope, distance, midpoint, the quadratic formula, exponent rules, special right triangles, SOH-CAH-TOA, and circle and volume formulas.
Does the ACT give you any formulas during the math section?
The ACT does not hand out a general formula sheet, but occasionally a specific formula or definition is printed inside a question stem when the problem depends on it. You should not count on that. Treat every standard formula as something you must already know, and read each question carefully in case a needed definition is supplied.
Which ACT Math topics are worth the most review time?
Algebra and coordinate geometry together account for the largest share of questions, followed by plane geometry and trigonometry. Statistics, probability, matrices, vectors, and complex numbers appear less often but are usually quick to review. If your time is limited, drill algebra and geometry first, then add the smaller topics as fast wins.
How do I stop running out of time on ACT Math?
Practice with a hard one-minute-per-question pace, and skip any question that stalls you for more than about 90 seconds so you can bank easier points first. Set up each calculation on paper before typing it into the calculator, and use the given measurements rather than trusting the diagram. After each practice section, sort your errors by cause so you fix patterns instead of single questions.