Why are decimals so hard in 5th grade? The 4 spots kids get stuck

By 15Q20M Editorial · Last updated September 17, 2026

Decimals are hard because they look like whole numbers but don't behave like them. A longer decimal can be smaller. Adding means lining up the decimal points. Multiplying can shrink a number and dividing can grow it. When a 5th grader struggles, the trouble usually sits in one of four spots, and a five-minute check points to which one.

Why are decimals so hard for kids who did fine with whole numbers?

By 5th grade, a child has spent years with whole numbers, and whole numbers teach some handy shortcuts. More digits means a bigger number. You line numbers up on the right. Multiplying makes the answer bigger. Those shortcuts worked for nearly every problem your child saw through 4th grade. Decimals are where they stop working, and the wrong answers they produce still look reasonable on the page.

Take a child who says 0.605 is bigger than 0.65. One common reason: 605 beats 65, so the child compares the digits the way they would for whole numbers. Vicki Steinle and Kaye Stacey, who tested 3,204 Australian students in Grades 4 to 10, called the consistent habit of choosing the longer decimal "longer-is-larger." In their data it was mostly a younger-student pattern that thinned out grade by grade. So a 5th grader making this mistake is in familiar territory, even though the study can't tell us how common it is in US classrooms today.

What 5th grade adds to the decimals your child saw in 4th grade

Your child met decimals in 4th grade as tenths and hundredths, mostly reading and comparing them. Fifth grade extends reading, writing, comparing, and rounding to thousandths, and it introduces all four operations with decimals to hundredths.

Two things in that table matter for homework. First, 5th grade does expect speed to build: the Grade 5 overview in the Common Core asks students to add and subtract decimals to hundredths fluently, and to multiply and divide them "efficiently and accurately." Second, the standard algorithm, meaning the vertical shortcut steps most parents learned, isn't named until 6th grade. A 5th grader who gets the answer with a drawing or a place value strategy, can explain why it works, and is getting quicker at it is on track.

The 4 places 5th grade decimals get hard

Why do decimals get bigger when divided?

Dividing a positive number by a decimal between 0 and 1 gives a bigger answer, because division asks how many times one amount fits into another. 3 ÷ 0.5 asks how many halves fit into 3. The answer is 6. Smaller pieces fit more times, so the count goes up.

Multiplying runs the same idea in reverse. 0.4 × 0.3 is four tenths of three tenths, a small piece of a small piece, so 0.12 makes sense and 1.2 doesn't. Our fractions guide walks through that "part of a part" idea, and it carries straight over to decimals.

A 5-minute check: which decimal skill is the problem?

These four questions come from our Grade 5 workbook. Write each one across the page, horizontally, so you don't line anything up for your child. Look at the work before you look at the answer. One question per skill can't prove anything on its own, so when something goes wrong, ask your child to explain it, then try two or three similar problems before deciding what to practice.

1. Put these in order from least to greatest: 0.6, 0.065, 0.605, 0.65. (Answer: 0.065, 0.6, 0.605, 0.65, so the greatest is 0.65.) If 0.605 lands at the top, ask why. "Because 605 is more than 65" points to comparing digits instead of place value, and that gap will show up in the other three skills too.
2. Solve 15.3 − 7.68. (Answer: 7.62.) If it's wrong, look at the setup first. Decimal points that don't sit in one straight column mean it's time to practice lining up by place value. Points lined up but the answer still wrong means the trouble is in the subtraction itself, often the borrowing, which is a different fix.
3. A student says 0.4 × 0.3 = 1.2. Is that right? (Answer: no, it's 0.12.) If your child agrees, ask how the decimal point got there. If the explanation is "4 times 3 is 12, then I moved the point one place," the work to do is decimal place value plus estimating: could four tenths of something be bigger than 1?
4. A student says 4.08 ÷ 4 = 1.2. Is that right? (Answer: no, it's 1.02.) If your child agrees, have them work it out themselves. If their own work skips the zero in the tenths place, practice holding each digit in its column while dividing, zeros included.

If the comparison question goes wrong, work on place value first, because all four operations lean on it. Then deal with whatever separate slip the other three showed. If only one of the other three goes wrong, practice that one.

How to help with decimals at home

Say decimals the long way. "Zero point six five" hides the meaning; "sixty-five hundredths" tells a child exactly what the number is. It also makes 0.65 versus 0.605 easier to think about: 650 thousandths against 605 thousandths.

Use money, but know where it stops. Dollars and cents model tenths and hundredths well, and a child who has counted change can see that $0.40 is more than $0.04. Ordinary dollars and cents stop at hundredths, though, so for thousandths reach for a place value chart or a number line. Number lines are worth using anyway: the federal practice guide on fractions instruction recommends them as a central tool, and it describes a study in which 5th and 6th graders practiced placing decimals on a line marked in tenths.

Estimate before calculating. For 3.6 × 2.5, ask: about how much is 4 × 2.5? Around 10. Now the exact answer, 9, looks right, and 0.9 or 90 look wrong. Estimating first gives a child a way to catch a misplaced decimal point on their own.

Give lining up a physical cue. Graph paper, one digit per box, decimal points in one column, keeps the setup honest. No graph paper in the house? Turn a sheet of lined notebook paper sideways and the lines become columns.

Keep practice short and spread out. A few problems a day for a couple of weeks lets you see whether the same error keeps coming back, which a single long review can't show you. Our own daily sets work this way: a fixed number of mixed problems on paper, scored in the free app, with an explanation for anything missed.

Try a free sample day: one full Grade 5 session, scored in the app

When 5th grade decimal trouble is really place value or fraction trouble

A decimal like 0.62 is a fraction, 62/100, written in place value columns instead of with a top and bottom number. That's why decimals and fractions in 5th grade tend to break in the same places. If your child can't say what 3/10 means, or can't explain why 0.5 and 1/2 are the same amount, work on that before more decimal problems. If the gap hasn't narrowed after a few weeks of practice, talk to the teacher.

Why fractions are hard in 5th grade, and how to help

If it's more than decimals: my 5th grader is struggling with math

Everything 5th grade Common Core math covers, domain by domain

Frequently asked questions