Point smoke & heat
Detector spacing calculator
Work out how many point detectors a room needs and where they go, with a scaled layout, wall offsets and spacings.
Free · No sign-up · Works on any device
Free tools for fire alarm engineers
Space detectors, size standby batteries, set DIP switch addresses and look up BS 5839-1:2025 — in seconds, on site or in the office.
- Based on BS 5839-1:2025
- Shareable results
- Same maths as the app
The tools
Everyday calculations, done properly
Built from the same calculations as the FireThings app, laid out for the big screen as well as the small one.
BS 5839-1 Annex E
Battery standby calculator
Check a panel's standby batteries against the Annex E minimum capacity, with the full working and the next size up if it fails.
Any 8-way switch
DIP switch address calculator
Flip the switches to read an address, or type an address to see which switches go on. Includes a printable 0–255 chart.
41 topics · searchable
BS 5839-1:2025 quick reference
Plain-English summaries of categories, siting, sounders, call points, cabling and testing — plus what changed in 2025.
Why use these tools
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Instant answers
Results update as you type. No account, no adverts and nothing to install.
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Works on any device
Designed for a phone on a ladder as much as a desktop in the office.
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Share a calculation
Every result has its own link — send it to a colleague or keep it with the job file.
The FireThings app
Take the tools on site
The free FireThings app puts these tools in your pocket, alongside the paperwork side of the job.
- Digital jobsheets with on-site signatures
- Fill in and share PDF forms
- Timestamp camera and decibel meter
- Works offline on site, syncs when you're back online
The app is free. Store links will appear here as soon as it's live.