8th Grade Math · Parent guide
What Math Should an 8th Grader Know?
Complete Parent Guide
By the end of 8th grade, your child should solve linear equations (including ones with no solution or infinitely many), solve systems of two linear equations, understand slope as a rate of change and write y = mx + b from a graph or a table, know what a function is, use exponent rules and scientific notation, work with square roots and irrational numbers, apply the Pythagorean theorem, describe rotations, reflections, translations and dilations, find volumes of cones, cylinders and spheres, and fit a line to a scatter plot. The Common Core names three focus areas for grade 8: expressions and equations (including systems), functions, and geometry with the Pythagorean theorem.
Reviewed against the Common Core standards.
What 8th Graders Learn in Math, by Domain
These are the Common Core State Standards for Grade 8 math, grouped by domain and put into plain English. Many states use them as written or in an adapted version, so your school's wording may differ slightly. The code after each skill is the standard it comes from, and each domain links to the full text on the Common Core site. Read the official Grade 8 introduction.
The Number System
Common Core 8.NS- Know that some numbers, like √2 and pi, are irrational, and that rational numbers have decimals that end or repeat (8.NS.1)
- Estimate irrational numbers and place them on a number line: √2 is between 1.4 and 1.5 (8.NS.2)
Expressions & Equations
Common Core 8.EE- Use exponent rules, including negative exponents: 3² × 3⁻⁵ = 1/27 (8.EE.1)
- Use square roots and cube roots to solve x² = p and x³ = p (8.EE.2)
- Read, write and compute with scientific notation (8.EE.3, 8.EE.4)
- Graph proportional relationships and read the unit rate as the slope (8.EE.5, 8.EE.6)
- Solve linear equations with variables on both sides, and recognize one, none or infinitely many solutions (8.EE.7)
- Solve systems of two linear equations by graphing and algebra (8.EE.8)
Functions
Common Core 8.F- Understand a function as a rule that gives exactly one output for each input (8.F.1)
- Compare functions shown as equations, tables, graphs and words (8.F.2)
- Know that y = mx + b makes a straight line, and give examples of functions that are not linear (8.F.3)
- Find the rate of change and starting value from a table, graph or description (8.F.4)
- Describe a graph in words: where it rises, falls or levels off (8.F.5)
Geometry
Common Core 8.G- Describe rotations, reflections, translations and dilations, including with coordinates (8.G.1-8.G.4)
- Use angle facts for triangles and parallel lines cut by a transversal (8.G.5)
- Explain and apply the Pythagorean theorem, including distance on a coordinate grid (8.G.6-8.G.8)
- Find volumes of cones, cylinders and spheres (8.G.9)
Statistics & Probability
Common Core 8.SP- Make and read scatter plots and describe patterns like positive or negative association and outliers (8.SP.1)
- Fit a straight line to data and judge how well it fits (8.SP.2)
- Interpret the slope and intercept of a line of fit in context (8.SP.3)
- Read two-way tables with relative frequencies (8.SP.4)
What 8th Grade Math Problems Look Like
Original practice problems written to match the standards above, with the answer and the thinking we would hope to hear.
System of equations (8.EE.8)
Two phone plans: Plan A is $20 a month plus $5 per GB. Plan B is $35 a month plus $2 per GB. At how many GB do they cost the same?
Answer: 5 GB. Solve 20 + 5g = 35 + 2g: 3g = 15, so g = 5. Both cost $45.
Slope and starting value (8.F.4)
A table shows a plant's height: week 0, 4 cm; week 2, 7 cm; week 4, 10 cm. Write an equation.
Answer: h = 1.5w + 4. The height grows 3 cm every 2 weeks, which is 1.5 cm per week, starting from 4 cm.
Pythagorean theorem (8.G.7)
A park is 6 blocks east and 8 blocks north of your house. How far is it in a straight line?
Answer: 10 blocks. 6² + 8² = 36 + 64 = 100, and √100 = 10.
Scientific notation (8.EE.4)
About how many times larger is 6 × 10⁹ than 3 × 10⁶?
Answer: 2,000 times. 6 ÷ 3 = 2, and 10⁹ ÷ 10⁶ = 10³.
Equations with no solution (8.EE.7)
How many solutions does 2(x + 3) = 2x + 5 have?
Answer: None. It simplifies to 2x + 6 = 2x + 5, which would mean 6 = 5.
Signs Your 8th Grader May Be Behind in Math
Eighth grade is the last year before high school math. These signs mean your child may struggle in algebra next year:
- !Cannot find the slope from two points, or confuses slope with the y-intercept
- !Can solve x + 5 = 12 but not 3(x - 2) = x + 8, where variables are on both sides
- !Thinks 2⁻³ is a negative number
- !Uses a² + b² = c² on triangles that are not right triangles, or puts the longest side in the wrong place
- !Cannot explain what the point where two lines cross means in a word problem
Short At-Home Activities (10 Minutes or Less)
Compare two plans
Pick two real offers, like two gym memberships with a sign-up fee and a monthly cost, and ask when they cost the same. That is a system of equations.
Play with a graphing calculator
Type y = 2x + 1 into a graphing tool and change the 2 and the 1. Ask your child to predict what the line will do before each change.
Find right triangles
Measure the width and height of a TV or laptop screen and use the Pythagorean theorem to check the diagonal size on the box.
Big and small numbers
Write distances from a science article or a news story in scientific notation, and compare two of them: how many times larger is one?
Scatter plot from your own data
Plot hours of sleep against how tired your child feels (1 to 10) for two weeks. Is there a pattern? Draw a line that fits.
Find Your Child's Exact Level
Eighth grade sets up high school algebra. Our diagnostic checks equations, functions, exponents and geometry, plus the earlier skills they depend on, in about 10 minutes.
Start the DiagnosticQuestions Parents Ask
Is 8th grade math the same as Algebra 1?
Not exactly. The Common Core grade 8 standards cover linear equations, systems of two linear equations, functions, exponents, irrational numbers and the Pythagorean theorem, along with geometry and statistics. Algebra 1 is a high school course that builds on this work. Some schools offer an Algebra 1 course in 8th grade instead, so ask which course your child is taking.
What is the most important skill in 8th grade math?
Linear relationships. Two of the three focus areas the Common Core names for grade 8 are linear equations and systems, and functions, and both depend on understanding slope as a rate of change (8.EE.5, 8.F.4).
My 8th grader can follow steps but freezes on word problems. What helps?
Ask your child to say what each number means before writing an equation: "the $20 is a fee you pay once, the $5 is per GB." Eighth grade standards ask students to interpret the rate of change and starting value in context (8.F.4), not just compute them.
Do 8th graders learn the Pythagorean theorem?
Yes. They explain why it works, use it to find missing sides in two and three dimensions, and use it to find the distance between two points on a coordinate grid (8.G.6-8.G.8).
Should my child be worried if 8th grade math feels much harder?
It usually feels harder because it combines earlier skills: fractions, negative numbers and one-step equations all show up inside 8th grade problems. If one of those is weak, fix it first; a diagnostic can show which.