Measuring with everyday things
Before you use a ruler, you can measure with things around you: paper clips, cubes, pencils, hand spans or footsteps. These are called non-standard units.
"The book is 8 paper clips long" is a measurement using a non-standard unit.
How to measure with units
- Choose a unit. All the units should be the same size, such as identical paper clips.
- Start at the end of the object.
- Lay units end to end in a straight line.
- No gaps between units.
- No overlaps: units must not lie on top of each other.
- Count the units.
- Say the number and the unit: "12 cubes long".
What can you measure?
| Measure | Example unit | Example |
|---|---|---|
| Length | paper clips, cubes | The pencil is 6 cubes long. |
| Height | blocks | The plant is 10 blocks tall. |
| Area | sticky notes | The desk is covered by 20 sticky notes. |
| Capacity | cups of rice | The jar holds 5 cups. |
| Mass | marbles on a balance | The toy balances 15 marbles. |
Why the unit matters
Measure a table with paper clips and you might get 40. Measure the same table with pencils and you might get 7. The table didn’t change. The unit did.
- Smaller units → bigger number.
- Bigger units → smaller number.
Why we need standard units
Your footsteps and a grown-up’s footsteps are different sizes. If you both measure the room, you’ll get different answers. That’s why people agreed on standard units like centimetres and metres, so everyone gets the same measurement.
Worked examples
Example 1: A shoe is 9 cubes long. What does that mean?
Nine cubes laid end to end, with no gaps or overlaps, match the shoe’s length.
Example 2: Ali measures a rug with hand spans and gets 10. Ali’s dad gets 7. Why?
Dad’s hand is bigger, so he needs fewer hand spans.
Example 3: Will you get a bigger number measuring a door with paper clips or pencils?
Paper clips are smaller, so the number will be bigger.
Common mistakes
- Leaving gaps between units: the answer comes out too small.
- Overlapping units: the answer is wrong too.
- Mixing different-sized units in one measurement.
- Forgetting to say the unit. "7" alone doesn’t tell us much.
Try it yourself
- Why should units touch end to end?
- You measure a pencil with cubes and get 8. Would you get more or fewer if you used paper clips that are longer than cubes?
- Name two non-standard units you could use to measure your desk.
- Why do people use standard units?
Answers: 1) So there are no gaps and the count is correct. 2) Fewer. 3) e.g. books and hand spans 4) So everyone gets the same measurement.
Quick recap
- Non-standard units are everyday objects used to measure.
- Lay them end to end with no gaps or overlaps.
- Different units give different numbers, which is why we use standard units.