3.MD.2: Measure Liquid Volume and Mass
Also written as 3.MD.A.2 and CCSS.MATH.CONTENT.3.MD.A.2 · Cluster: Solve problems involving measurement and estimation.
The Official Wording
Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l). Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem.
Common Core State Standards, Grade 3, Measurement & Data · Read it at the source · Checked October 14, 2026
What 3.MD.2 Means in Plain English
Third graders learn grams, kilograms and liters by holding them: a paper clip is about 1 gram, a dictionary about 1 kilogram, and a large water bottle holds 1 liter. Then they read scales and beakers and solve one-step problems: 3 jugs of 4 liters is 12 liters.
Every problem stays in one unit and one step, with no “twice as heavy” comparisons. Converting kilograms to grams or liters to milliliters waits for 4th grade (4.MD.1), along with word problems that mix units (4.MD.2).
3.MD.2 I Can Statements
- I can estimate whether something is about a gram or a kilogram.
- I can read the liters on a beaker or jug scale.
- I can solve one-step word problems about grams, kilograms and liters.
3.MD.2 Worked Example
The class fish tank filled bucket by bucket, drawn as a beaker with a scale the way the standard suggests.
The class fish tank holds 32 liters of water. Mr. Diaz fills it with a bucket that holds 4 liters. How many full buckets does it take?
- Estimate first. 32 liters is a little more than 30, and 30 liters is about 7 or 8 buckets of 4.about 8 buckets
- Draw the tank as a beaker with a scale from 0 to 32 liters. Each bucket raises the water by 4 liters, so mark the scale every 4.0, 4, 8, 12, up to 32 liters
- Count the buckets as jumps up the scale until the water reaches the top line.4, 8, 12, 16, 20, 24, 28, 32: 8 jumps
- That count is a division: how many 4s make 32?32 ÷ 4 = 8
Check it: Multiply back: 8 buckets × 4 liters = 32 liters. Every number was in liters, so nothing needed converting, and 8 matches the estimate.
Common Mistakes with 3.MD.2
Bigger means heavier
A beach ball estimated at 3 kilograms and a small bag of sand at 100 grams
Try this: Pass both objects around and let students feel them before estimating. Bigger is not always heavier, and the balance scale settles it.
Reading every mark as 1
A beaker marked every 2 liters, water at the fourth mark, read as 4 liters instead of 8
Try this: Have students read the labeled numbers first and work out what each jump between labels is worth before reading the water level.
Grams and kilograms swapped
“My backpack is 4 grams” or a pencil estimated at 5 kilograms
Try this: Keep a benchmark shelf: a paper clip for 1 gram and a 1-liter bottle of water for 1 kilogram. Compare every estimate to them.
Where 3.MD.2 Fits
Practice 3.MD.2
Quick Check
- Which unit fits the mass of a watermelon better, grams or kilograms?
- Three bags of flour have a mass of 5 kilograms each. What is their total mass?
- A box of crayons has a mass of 450 grams and a bottle of glue 175 grams. How much heavier is the crayon box?