Door and Window Sensor Calculator
A magnetic reed contact guards every opening — but a double, French or wide sliding unit has more than one moving leaf, so it needs a contact per leaf. Enter your openings to get the total contacts to buy, the openings protected, and a suggested wired or wireless zone count. Planning figures; runs in your browser.
- Single-leaf doors & windows1 contact each
- Double / French & wide sliding leaves1 per moving leaf
A very wide sliding run can need an extra contact where a leaf slides past the frame — add one in the count above if in doubt.
Planning estimate only — verify with the product datasheet and a site walk-through. Prefer recessed contacts for a clean finish, and test the gap spec (typically 15–20 mm) against the actual door on install so the magnet and reed still register when the leaf is shut.
Related Guides — Deep-dive reading
Window Sensors in India (2026): Placing Contact Sensors on Sliding, Casement and Grilled Windows
How magnetic window contact sensors detect a window being opened, why that is different from a glass-break sensor, and exactly where to fit them on the sliding, casement and grilled windows found in Indian homes.
SecurityDoor Sensors in India (2026): The Contact Sensor That Starts Every Alarm
How a door contact sensor works, wired versus wireless, surface-mount versus recessed, exactly where to place it, which doors to cover in an Indian home, and the honest limits worth knowing before you buy.
SecurityGlass-Break Sensors in India (2026): Catching a Smashed Pane Before Entry
How acoustic glass-break sensors listen for the twin sound of breaking glass, why they cover what door and window contacts miss, and how to place one sensor to protect a whole room of windows in an Indian home or shop.
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Plan acoustic glass-break sensors for heavily-glazed rooms where a contact on every pane is impractical. Enter the rooms with glass, their size and the sensor's listening radius to get how many you need. A planning estimate; verify line-of-sight and range on site.
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