This challenge is now closed – check out our winners below!
To celebrate the recent expansion to the range of SI prefixes, (for the first time in 31 years!) we challenged primary and secondary school pupils to come up with two mnemonics (how to create a mnemonic) to help remember the names of all the SI prefixes.
We are pleased to announce our winners as:
Primary School category: Alice from Twickenham Preparatory School
Large range: Dogs hate kissing monkeys given that primates eat zesty yuzus rather quickly
Small range: Delightful cats mostly meow nicely purring furiously and zealously yet rarely quietly
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Secondary School category: Alexa from Beaulieu Convent School
Large range: Dizzy Hot Koalas Mainly Get Tired Patiently Eating Zesty Yellow Round Quinces
Small range: Drunk Chunky Monkeys Munch Nutty Peanut Fudge After Zebras Yell Rude Questions
We are pleased to announce our runners up as:

Primary School category: Sandra from Beaulieu Primary School
Large range: Daydreaming Hippos Kindly Make Granola Tiramisu Pleasing Each Zebra Yelping Romantic Quotes
Small range: Do Crazy Male Magpies Need Protection From All Zebras Yelling Ridiculous Questions?

Secondary School category: Dorian from Lord Wandsworth College
Large range: During His Kingdom's Mighty Growth, The Prince Enjoyed Zooming on Yellow, Racing Quadbikes
Small range: Dangerously Crossing Mountains Means Navigating Precisely. Find A Zipline, Yell "Rescue!" Quickly!

Entries now closed
For submissions to be judged, they will need to be shared with NPL by an adult.
- Submit your entry using the form below.
- Please only put your first name on entries (no surnames).
- Entries close midnight Tuesday 28th February 2023.
- We will only accept entries with a responsible adult’s contact details.
- Winners will be chosen by a panel of judges at NPL.
- From 6 March 2023, the responsible adult for each winner and runner up will be notified by email and a selection of entries posted on the NPL website.
- Winners will receive £200 worth of high-street gift vouchers. Runners up will receive £50 worth of high-street gift vouchers. We will share the best entries on our webpage and feature them on our social media channels including Instagram, Facebook and Twitter.
- If you like, share your creative entries on social media using #SIprefixchallenge where you can go beyond words and present your entry as a video, animation, song or rap.
Challenge rules
- The challenge is open to all UK school age children with two judging categories: Primary and Secondary.
- Entries must be shared with NPL by a responsible adult (who could be a teacher or parent/carer).
- Ideas involving derogatory comments, dangerous activities, inferred harm to living creatures or rude language are not acceptable.
- Entries must not contain any private and confidential information.
- The challenge will run between 21 November 2022 and 28 February 2023 (inclusive) and only entries received in this period will be accepted and considered.
What is an SI prefix? And why are they important?
There is a worldwide agreement between all countries to measure using the International System of Units (SI). Prefixes in this system represent multiples or subdivisions, and make it easier to understand and communicate when numbers get very big or very small.
The internationally agreed SI prefixes can be combined with every SI unit of measurement, for example:
| Prefix Name | Prefix Symbol | Multiplier | In practise |
| milli | m | one thousandth | millimetre (mm) = 0.001 metre = 10-3 metre |
| milligram (mg) = 0.001 gram = 10-3 gram | |||
| kilo | k | one thousand | kilometre (km) = 1000 metre = 103 metre |
| kilogram (kg) = 1000 metre = 103 metre |
For this challenge we asked participants to create two mnemonics, one for the SI prefix names for big numbers, and one for the SI prefix names for small numbers. You can see both in the chart below.
| Multiplying Factor | Name (symbol) | Scientific Notation |
| 1 000 000 000 000 000 000 000 000 000 000 | quetta (Q) | 1030 |
| 1 000 000 000 000 000 000 000 000 000 | ronna (R) | 1027 |
| 1 000 000 000 000 000 000 000 000 | yotta (Y) | 1024 |
| 1 000 000 000 000 000 000 000 | zetta (Z) | 1021 |
| 1 000 000 000 000 000 000 | exa (E) | 1018 |
| 1 000 000 000 000 000 | peta (P) | 1015 |
| 1 000 000 000 000 | tera (T) | 1012 |
| 1 000 000 000 | giga (G) | 109 |
| 1 000 000 | mega (M) | 106 |
| 1 000 | kilo (k) | 103 |
| 100 | hecto (h) | 102 |
| 10 | deca (da) | 101 |
| 1 | 100 | |
| 0.1 | deci (d) | 10-1 |
| 0.01 | centi (c) | 10-2 |
| 0.001 | milli (m) | 10-3 |
| 0.000 001 | micro (µ) | 10-6 |
| 0.000 000 001 | nano (n) | 10-9 |
| 0.000 000 000 001 | pico (p) | 10-12 |
| 0.000 000 000 000 001 | femto (f) | 10-15 |
| 0.000 000 000 000 000 001 | atto (a) | 10-18 |
| 0.000 000 000 000 000 000 001 | zepto (z) | 10-21 |
| 0.000 000 000 000 000 000 000 001 | yocto (y) | 10-24 |
| 0.000 000 000 000 000 000 000 000 001 | ronto (r) | 10-27 |
| 0.000 000 000 000 000 000 000 000 000 001 | quecto (q) | 10-30 |
Here’s an example of mnemonics we have come up with to get you started…
| Daringly | hungry | kangaroos | mock | gorillas | that | playfully | eat | zucchini | yet | rarely | quarrel |
| deca | hecto | kilo | mega | giga | tera | peta | exa | zetta | yotta | ronna | quetta |
| Did | centipedes | munch | my | noodles? | Please | find | all | zingy | yellow | racoons | quickly |
| deci | centi | milli | micro | nano | pico | femto | atto | zepto | yocto | ronto | quecto |
What is a mnemonic?
A mnemonic is a system such as a pattern of letters, ideas, or associations which assists in remembering something. For example, you may have used a mnemonic before to remember the correct the order of the colours of the rainbow, or the order of the planets in space.
| Richard | of | York | gave | battle | in | vain |
| Red | Orange | Yellow | Green | Blue | Indigo | Violet |
| My | very | easy | method | just | speeds | up | nothing |
| Mercury | Venus | Earth | Mars | Jupiter | Saturn | Uranus | Neptune |
| Did | centipedes | munch | my | noodles? | Please | find | all | zingy | yellow | racoons | quickly |
| deci | centi | milli | micro | nano | pico | femto | atto | zepto | yocto | ronto | quecto |