StandbyCalc
UK standby battery calculator for fire and intruder alarm systems. BS EN 50131 and BS 5839-1:2025 compliant.
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Everything you need on site
Intruder Alarms
BS EN 50131 / BS 9263 compliant. Grades 1–4 with automatic standby and alarm period selection. ARC mains-fail signal support.
Fire Alarms
BS 5839-1:2025 compliant. Categories L, M, and P. Occupancy, generator backup, and configurable de-rating factor.
Standalone PSU
Custom standby and alarm periods. 12V or 24V systems. Perfect for signalling devices, access control, and CCTV backup power.
Instant Results
Full calculation breakdown showing the formula, standby load, alarm load, ageing factor, and recommended standard battery size.
PDF Reports
Generate professional A4 reports with full formula working. Add your company branding and logo. Share via email or AirDrop.
Save & Sync
Save unlimited calculations locally. Pro users get iCloud sync across all devices. Swipe to delete, tap to review.
Built to British Standards
Calculations follow published British Standards and are compliant with NSI and SSAIB requirements.
Free on the App Store
Free to download and use. One-time Pro upgrade unlocks PDF reports with company branding and iCloud sync across all your devices.
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