Fiducia TogetherBinary and hexadecimal
Counting in twos and sixteens, and converting between them and decimal.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Binary is base 2, using 0 and 1. Hexadecimal is base 16, using 0-9 and A-F. Computers work in binary; hex is a shorthand for humans, since one hex digit is exactly four bits.
Where it applies
GCSE and A Level computer science.
How it works
Place values in binary are 128, 64, 32, 16, 8, 4, 2, 1 for a byte. Conversion to decimal is adding the place values where there is a 1.
Binary addition carries at 2. An overflow error occurs when a result needs more bits than are available.
How to use it in your work
Write the place values above the digits before converting. It takes five seconds and prevents most errors.
Show your working for conversions — method marks are available.
For hex, convert via binary in groups of four bits rather than dividing by 16.
Where to get help
Your teacher and your board's specification — the pseudocode and the required language differ between boards. Bitesize covers the concepts; the computer science song runs the topics.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Computer Science Song The GCSE computer science topics, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.