Why measurement doesn't work like other math topics
Four is always four. Addition and counting hold still no matter who's doing them or what they're using. Measurement doesn't work that way. It's comparative, and it depends entirely on the unit you pick, so 'how long is this' becomes the first math question in your child's life where the honest answer is 'it depends what you're measuring with.' That's a genuinely different kind of thinking than anything a first or second grader has done with numbers before.
A child who breezes through addition worksheets can stall completely on a measurement page, and it's not because the numbers are harder. The skill being tested is different: taking an abstract figure like 20 cm and mapping it onto something physical you could actually hold. Arithmetic asks a child to manipulate symbols. Measurement asks them to translate between symbols and the world, and that translation step is where most six- and seven-year-olds get stuck.
This matters for how you help. Drilling more measurement problems on paper doesn't fix a translation problem, more physical reference points does. A child who has held a 30 cm ruler against a real tape measure, or watched a liter of water fill four regular drinking glasses, has something to translate to. A child who has only seen numbers on a page doesn't.
Start comparative, before introducing units
Before centimeters mean anything at all, a child needs 'longer than,' 'shorter than,' and 'about the same as' locked in first. Lining up two pencils on the table and pointing to the longer one is the real foundation here, not the ruler. Skip this step and the unit becomes a word to memorize rather than a way of seeing.
The same logic applies to weight and volume. Hand your child two apples, one in each hand, and ask which feels heavier. Pour water into two mismatched cups and ask which has more. These comparisons, done with zero numbers involved, build the sense that units will later put language to.
One mistake parents make here: pulling out the ruler too early because the worksheet happens to have one drawn on it. A child who can't yet reliably say which of two objects is longer won't get more out of a ruler, they'll just learn to read off a number without understanding what it represents. Wait until longer/shorter/same comes out automatically, usually somewhere around age 5 or 6, before numbers enter the picture at all.
Connect worksheet units to objects your child already knows
A worksheet answer of 15 cm doesn't mean much sitting alone on a page. Anchor it to something familiar: “that's about as long as your hand.” Now the number has a physical reference your child can actually check.
This is where the kitchen earns its keep. Measuring cups are one of the best measurement tools already in your house, because a 3-year-old can pour a cup of rice into a 2-cup measure and see, immediately, that it doesn't fill it. Say something like “let's see how many of these little cups it takes to fill the big one” while you're making pancake batter on a Saturday morning, and you've turned breakfast into a volume lesson without a worksheet in sight.
Keep a small set of real tools within reach: a ruler, a kitchen scale, a set of measuring cups. Let your child measure a snack, a toy, or their own height every so often, not as a lesson, just as something to do. A number they measured themselves lands completely differently in memory than a number printed on a page.
Building estimation before precision
Ask your child to guess a length or weight before measuring it. Say “how many of your footsteps do you think it'll take to cross the kitchen? Let's find out.” Estimating first, even when the guess is way off, builds a working sense of scale that measuring alone never does.
Track a handful of these guesses over a few weeks, even just in your head. You'll see your child's estimates creep closer to the real number. That narrowing gap, not any single correct worksheet answer, is the actual sign the skill is taking hold.
Common mixed-up units, and how to untangle them
Milliliters versus liters, grams versus kilograms — kids mix these up constantly, and it's rarely a math problem. It's a missing physical feel for how big the gap actually is. Set a liter bottle of water next to a single milliliter, a few drops in a spoon, and the gap becomes obvious in a way no number line ever makes it.
When your child gets a conversion wrong, resist the urge to just redo the calculation with them. Ask them to picture or go find the real object first. Fix the physical intuition and the math error usually straightens itself out along with it.
Where worksheets fall short
Worth saying plainly: worksheet practice alone will not build this skill. A child can fill out twenty pages of unit conversions correctly and still have no real sense of how big a kilogram is. Worksheets are useful for practicing the notation and the arithmetic that comes after the physical sense is already there. They're a follow-up, not a starting point.
If your child gets measurement answers right on paper but seems oddly unsure in real life, guessing a whale weighs about the same as a car, say, that's not a red flag. It's completely normal at age 6 or 7. It is a sign to spend more time with real objects, though, not more time with worksheets.