The purpose of the estimation jar is not only to practise counting and problem solving but to develop curiosity about numbers and maths. What might sound like a simple guessing game (and, really, it is that simple) takes on levels of complexity as your child grows and develops.

estimation jar for mathematics

For this activity, you’ll need a variety of things to put into a clear jar; the younger the child, the bigger the object (like Easter eggs or ping pong balls)—making it easier for little ones to succeed in their estimates. The older the child, the smaller the object (like marbles, game pieces, beads etc.). A handy tip is that colour differentiation makes it easier for children to guess ‘how many’ is inside the jar. Watch the below presentation by My Montessori Works:

What is particularly great about the Estimation Jar application is that it can be used from age 3 up until age 13. Put the filled jar on a shelf; anyone participating writes down their guess. then count the total at the end of the week. Little ones will want to explore the jar, holding it and peering inside, before making their guess, and older children will be able to use logical problem-solving skills, like: if 10 beads fit into 1 square inch, how many square inches makes up the jar and therefore how many beads are likely to be in the jar?

Once children have all made their guess and it’s time to open up and count, take the opportunity to practise counting with little ones as each object is removed. With older children, count in multiples; ask them to group the beads (or whatever small item fills the jar) in piles of 5/10—and count in multiples.

Jars could be themed according to season or celebration—and feel free to include estimation work in practical life activities: “Is there enough water in this jug for all 5 of you to have a cup?” or “Do we have enough spoons for everybody at the table?”.

And remember, estimating isn’t coming up with the exact answer, it’s a good guess.

If you’d like further information about this tutorial, feel free to contact us at We’re happy to answer any questions.