Counting

Counting is how we answer the question “how many?”. How many toys are in the box? How many stairs to the top? How many sweets in the jar? Every time you want a number for a pile of things, you count them.

The trick is simple but powerful: point at each thing once and say the number names in their special order — one, two, three, four, five, … — never skipping one and never saying the same one twice.

This is the very first root of the tree of knowledge — almost everything else in mathematics grows from being able to count.

Not at all! You can count anything. Three ducks a duck a duck a duck are exactly the same amount as three frogs a frog a frog a frog. The number 3 doesn't care whether it is counting ducks, frogs, stars or stairs — “three” always means the same amount.

One thing, one number

Watch the frogs. Each time a new frog hops in, we say the next number. One frog, one number — the count goes up by exactly one every single time. That is the heart of counting: one-to-one. Touch a thing, say a number; touch the next thing, say the next number.

Touch and count

Here is a pile of counters. Touch each one with your finger and say its number out loud: the little number under each counter is the one you say as you reach it. The very last number you say is the answer. Press Refresh for a brand-new pile to count.

Count along a number line

Numbers also live in a row called a number line. Counting is just hopping along it, one step at a time. Each hop is “one more”. Press the steps to hop from 1 all the way to 10.

Count in a ten-frame

A ten-frame is a box with two rows of five. We fill it from the top-left, one dot at a time. It helps you see a number without counting every dot from the start — your eyes learn what “seven” looks like. Count the dots below:

The last number is “how many”

Here is the most important secret in counting: the last number you say tells you how many there are. You don't have to count again — the final word is the answer.

Count these ducks with your finger:

duck one duck two duck three duck four

“One, two, three, four.” The last word was four, so there are 4 ducks.

Now the birds:

bird one bird two bird three

“One, two, three.” So there are 3 birds — even though birds and ducks look nothing alike, “three” and “four” mean the same amounts every time.

The two traps that trip up every new counter:

Zero! Zero means “none at all” — an empty box, no frogs, nothing to count. We start saying number names at one because we only count things that are actually there, but the number line really begins at 0.

Forever! However big a pile of stars a star a star a star you have, you can always add one more star and say one more number. There is no biggest number — you would never run out, no matter how long you counted.

See it explained