Engineer Tools
Free tools for fire and security engineers.
Calculators, checkers, reference pages and printable sheets for fire alarm, intruder alarm, emergency lighting, extinguishers, CCTV and access control. Each calculator shows its working, and each one works on a phone. No sign-up, no email address.
Quick reference guidesSearch the standards for the answer you need, in plain language, with a plain-terms switch. Or paste some jargon into "Explain this text".
Download the tools to use with no signal
Open this page once with a signal and the whole set of tools and guides downloads to your device by itself, so it works in a plant room or a basement. Nothing to install from a store. Add it to your home screen to open it like an app.
On an iPhone or iPad: tap the Share button in Safari, then "Add to Home Screen".
The downloaded copy updates itself whenever you open the site with a signal. The version date shows how current it is. The demo request form still needs a signal.
Fire alarm
9 tools
Fire alarm battery calculatorMinimum standby battery capacity from the standby and alarm current, with the full working shown.Fire alarm sounder circuit calculatorCheck the last sounder still gets enough voltage, and find the longest cable for the load.Fire alarm detector spacing calculatorA planning count of smoke or heat detectors for a rectangular room, with the ceiling height limit checked.Fire alarm sound level checkerThe minimum alarm sound level for an area, allowing for background noise, and a check of your reading.Fire alarm zone checkerThe fewest zones a storey needs, and a check of a zone's floor area and search distance.Manual call point distance checkerCheck the distance to a manual call point (45 m walking, 30 m straight line) and its mounting height.Fire alarm system categoriesWhat L1 to L5, M, P1 and P2 mean, and what changed in the 2025 edition.Fire alarm log bookSystem details, weekly test record, events log and service visits, ready to print and fill in.Fire alarm service visit checklistA checklist to print and carry on a service visit, in the order of the visit.
Intruder alarm
2 tools
Emergency lighting
4 tools
Emergency lighting test due date calculatorWhen the next monthly, annual or five-yearly emergency lighting test is due.Exit sign viewing distance calculatorHow far an exit sign can be read from, from the height of its pictogram.Emergency lighting lux checkerCheck a reading against the minimum lux for escape routes, open areas, fire equipment and high-risk areas, and check uniformity.Emergency lighting log bookMonthly and annual test records, photometric checks and repairs, ready to print and fill in.
Fire extinguishers
3 tools
Fire extinguisher numbers calculatorHow many extinguishers a storey needs from its floor area and the extinguisher's Class A rating.Fire extinguisher service due date calculatorThe next basic, extended or CO2 overhaul service date from the date of the last one.Fire extinguisher type guideThe colour band for each extinguisher type, what it is for, and what it must not be used on.
CCTV
4 tools
CCTV pixel density calculatorPixels per metre at the target, the highest level it meets, and how close you need to be for the next. 2025 and 2015 levels.CCTV lens and field of view calculatorField of view from the lens and sensor size, and the width and height of the scene at a distance.CCTV storage and bandwidth calculatorDisk space and network load from the number of cameras, bitrate and days kept.PoE budget calculatorCheck the devices on a PoE switch fit its power budget with headroom, and flag any too hungry for the port.
Access control
3 tools
Access control lock cable calculatorCheck a door lock still gets enough voltage at the end of its cable, and find the longest run.Access control door power supply calculatorSize the power supply for a door from the locks, readers and controllers on it, and work out battery standby time.Fail-safe and fail-secure locksWhat fail-safe and fail-secure mean, where each is used, and the three BS 7273-4 categories.
General electrical
6 tools
DC voltage drop calculatorVoltage lost along a two-wire DC cable from its size, length and current, with the longest run for a drop you choose.Ohm's law and power calculatorVoltage, current, resistance and power from any two of them, with the working shown.Which certificate do I need?Which certificate goes with a fire alarm or emergency lighting job, and who signs it.Electrical unit converterMilliamps and amps, milliamp hours and amp hours, metres and feet, millimetres and inches.UK fire and security standards: current editionsThe current edition of the standards engineers use most, with the date the list was last checked.Fire and security glossaryWhat ARC, CIE, MCP, lux, PoE and other terms mean. Searchable.
For guidance only. Always check against the current edition of the standard and the manufacturer's data.
Built by the engineer behind Kerova, certificate software for fire and security firms.