How Many Motion Sensors Do You Need? (Expert Opinion)

As you begin to secure your residence, one thing you should be careful of is installing ‘too many’ motion sensors. But again, what’s the ideal limit to installing motion sensors? Read ahead as we answer your query on ‘how many motion sensors do I really need?’! 

How Many Motion Sensors Do I Need?

Most motion sensors today cover anything from a small cabin to a fairly spacious room. With increase in coverage and field of view, you don’t need multiple motion sensors in a single hallway or room. A single sensor per area should suffice for security (without the increased risks of false alarms).

To effectively figure out how many motion sensors you need – start off with the layout of your home. Identify all hallways, rooms, and entryways. Divide areas into spaces while considering shared spaces as a single ‘area’ of the house.

This should give you a quick idea as to where common installation spots might be. 

Traditional Passive Infrared motion sensors can detect objects at a distance of approximately 25 feet. You should prioritize installing the sensors at the corners of the room. This side-to-side motion detection helps it cover a larger area while staying hidden (not always). 

Now that you have an idea as to how a motion sensor works and have the layout of your home. Start identifying common spots of installation such that each valuable area and entry point is covered without repetitions.

Shared spots only require a single sensor to be installed at the entry point. Similarly, shared hallways and stairs are excellent spots to cover entry to other floors of your residence. However, you should be careful of the mount point and angle as a lower angle and height could raise false alarms on a pet you might be fostering. 

False alarms aren’t the only drawback to installing excessive motion sensors. Let’s explore what drawbacks you’re bound to face if you do go ahead with installing a few too many sensors at your residence.

What Are The Drawbacks Of  ‘Too Many’ Motion Sensors

The expense of purchasing a sensor and its labor-intensive installation might add to your troubles if you install too many motion sensors. Not to mention, you’ll quickly exhaust yourself from debugging false alarms from these sensors. Let’s explore each one of these drawbacks in a little more detail.

False Alarms

One thing’s for sure – there’s no workaround for false triggers in motion sensors. However, installing multiple sensors only ensures you’re increasing the number of triggers at a particular time. Although there’s a chance for it to be threatening, mostly, these alerts are caused by curious pets or children out for a snack.


Although motion sensors are easier to install than several other security products, it’s still a labor-intensive task to install them. Once placed, they’ve to be configured so the sensitivity isn’t a problem for you soon after. Again, the more sensors you choose to install, the more trial and error you go through.


Every motion sensor would, obviously, be adding a few bucks to your overall expense. Although sensors are cheaper with complete packages, you’d be overspending on buying the additional sensors you’re going to place.

If you ask us for an opinion – save on the additional motion sensors and go for security cameras or contact sensors for a more diverse approach towards home security. 

Frequently Asked Questions on How Many Motion Sensors You Need

We’ll leave you to decide how many motion sensors you really need. But to help you make this decision, we’ve got a short section on frequently asked questions on installing motion sensors. Read ahead as we answer some of these questions (might even clear some confusions you yourself have).

Where is the best place to put a motion sensor?

The best place to put a motion sensor is the corner of a room such that the side-to-side coverage ensures no entry point is missed. Often, corner-mounted motion sensors are missed by people entering the room allowing the sensors to stay undetected. You should cover master bedrooms, living rooms, and entrances the same way.
Remember – don’t mount your motion sensor at a low height or a depressed angle. Curious kids and pets might falsely trigger the sensor causing you unnecessary trouble. To avoid these false triggers, mount the sensor such that it is only triggered on humans. Set the sensitivity accordingly.

Do I need sensors on every window?

It is ideal to place contact sensors on every window of your house. However, these sensors, most probably, won’t go off if the intrusion isn’t attempted by breaking or entering through a window. That’s because contact (window) sensors work differently than motion sensors. These typically detect movement of the glass and raise alarms if that happens which can detect intruders while they’re at their attempt.
However, as we’ve discussed before, if the window is bypassed completely, these sensors won’t trigger. Therefore, window sensors should be complemented with motion sensors and security cameras for better surveillance.

Do I need motion sensors upstairs?

Ideally, you should install motion sensors at every entrypoint of your house including upstairs windows. Install a motion sensor near the shared hallway or stairs along with a window sensor on any window you might have for better security. 
It’s common to think or feel burglars won’t choose upstairs as the intrusion point. But that’s a mistake. You should secure all windows and entry points to other floors just as you’d secure your ground floor for maximum security.

That’s it folks. Concluding our take on how many motions you really need, you should ideally be going for a single sensor per room or shared area. This will ensure every key area of your residence is covered and you have the least number of blindspots available. So, how many motion sensors does it take?