What is estimating?

  • Estimating is used to help us predict the answer to a calculation.

  • We use estimation to make calculations more manageable.

How does it work?

Estimating is when we take one or more numbers in a calculation and round them to a number that is closest to the original number. We can round down or up, depending on the situation. We usually round to the nearest 5 or 10.

We round numbers in calculations to make it easier to calculate either in our heads or with a pen and paper. It can be useful to have an estimation when planning something in advance.

In the video we see how estimation can be used to predict the amount of ingredients needed for an event.


The video shows that 0.75 kg of tomatoes are needed for 10 people. To estimate how much produce to buy for the full party of 70 people, we need to multiply 0.75 by 7:

0.75 × 7 = 5.25 kg

This tells us that we need at least 5.25 kg of tomatoes. The manager adds an extra 10% on to the total in case some of the tomatoes are squashed or damaged, and rounds up to 6 kg.

This is only an estimate as it is not always possible to predict exactly how many tomatoes are required.

Where is this useful?

Estimation is not only used in catering but also in project management and the construction industry.

Where next?

Discover more about this topic from around Bitesize.

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How to use BIDMAS to solve equations
How to solve algebraic equations using guess and check