Virtual measuring jug

What the jug shows

A measuring jug has a scale up the side for reading how much liquid it holds. On this page, hold Hold to pour to pour water in, and Hold to pour out to tip it out. The +10 mL and −10 mL buttons make small, exact changes. Jug A holds 1,000 mL, which is 1 liter, with a line every 50 mL and a number every 100 mL. The scale can show milliliters, US cups marked in quarters, or both.

Compare two jugs adds jug B, which holds 500 mL. It is narrower, so its lines are spaced further apart: 200 mL looks taller in jug B than in jug A. The amount is hidden at first, so children read the scale; Show the amount reveals it in milliliters and cups. Challenges include pouring 350 mL, pouring 1½ cups and making two jugs hold the same amount, each with a Check button.

Why read a scale by pouring

Reading a capacity scale means working out what each unlabeled line is worth, then counting on from the nearest number. Pouring makes the reading active: the child has to stop at the right line, which builds estimation as well as reading. Comparing two jugs of different widths tackles a strong misconception, that the higher water always means more. Common Core introduces liquid volume in liters in grade 3 (3.MD.A.2) and milliliters in grade 4 (4.MD.A.1).

Common mix-ups

• Thinking every line is worth 1 mL or 100 mL. Check how many spaces there are between two numbers first. On jug A each space is 50 mL; on jug B each is 25 mL.
• Judging by height alone. In a narrower container the same amount of water stands taller.
• Reading from above. Look straight across at the water level, not down from the top.
• Assuming a cup is a round number of milliliters. A US cup is about 237 mL.

A 10-minute capacity routine

• Ask what each small line on jug A is worth before pouring anything.
• Pour to 300 mL, then to 750 mL, reading the scale aloud each time.
• Press Challenge and let the child pour and check.
• Switch to Compare two jugs and pour the same amount into both. Ask which holds more.
• Finish by turning on the cup scale and finding where 2 cups is.

Where it fits by grade

• Grades 1 and 2: compare which container holds more and practice reading simple scales.
• Grade 3: measure and estimate liquid volumes in liters (3.MD.A.2).
• Grade 4: know that 1 liter is 1,000 milliliters and solve problems with liquid volumes (4.MD.A.1 and 4.MD.A.2).
• England: Year 2 measures capacity in liters and milliliters with measuring vessels, Year 3 measures, compares, adds and subtracts volumes, and Year 4 converts between units.

Learning more

Place value and number line skills sit underneath scale reading, and both are on Eurekami's skill map. Daily Practice brings skills back when they start to fade, and teachers can print worksheets with answer keys.