Decimal Builder

Choose a mode

Fill the ones, tenths and hundredths jars with the − / + buttons (each jar's sand level shows that digit), then press Check

3D math game · Best for grades 4-5

Decimal Builder

Decimal Builder puts students in a lab where three sand jars represent ones, tenths, and hundredths. They fill each jar to the correct level to construct a target decimal, turning abstract place-value notation into a visible, physical quantity they can read at a glance.

What students practice

Decimal Builder develops decimal place value: students practise reading each digit's column (ones, tenths, hundredths) and translating it into a physical quantity. This is the foundational step before comparing, ordering, or adding decimal numbers.

  1. Read the target decimal shown above the jars.
  2. Use the ones jar's +/- buttons to set the digit before the decimal point.
  3. Use the tenths jar to set the first decimal digit, and the hundredths jar for the second.
  4. The sand level in each jar shows the current digit — adjust until all three match the target.
  5. Press Check to confirm your number.

How to use it at home or in class

For the target 2.35: fill the ones jar to 2, the tenths jar to 3, and the hundredths jar to 5. Seeing three separate jars side by side makes the structure 2 + 0.3 + 0.05 obvious before any arithmetic is attempted.

Students often treat decimals as whole numbers, entering 35 into the hundredths jar for 0.35. Separate jars with individual levels force them to work one column at a time, breaking the habit of reading across the decimal point without pausing.

Use it for individual practice, paired work, or a short class demonstration before worksheets.

Start with the game above, then continue with written practice to reinforce the skill.

Common questions

How do the sand jars show decimal place value differently from the block columns in Place Value Builder?
Place Value Builder uses stacking blocks for whole-number hundreds, tens, and ones. Decimal Builder uses sand-fill jars for ones, tenths, and hundredths, making the fractional columns visible without blocks.
Which grades is Decimal Builder for?
Grades 4-5, where students first meet tenths and hundredths as named place-value positions.
Can students set a digit greater than 9 in any jar?
No. Each jar is capped at 9, so the game keeps students within standard decimal notation and avoids the carrying step handled separately in Decimal Addition.