What side view mirrors do and why they matter
A side view mirror is a mirror mounted on the outside of your vehicle's door that shows you what is happening to the sides and behind your car. Unlike your rearview mirror, which shows what is directly behind you, side mirrors let you see the lanes next to you and catch movement you would miss if you only looked straight ahead or in your rearview mirror.
Side mirrors are required by law in most places because they fill a blind spot — an area around your vehicle that you cannot see by looking forward or in your rearview mirror alone. When you change lanes, merge onto a highway, or back up, a side mirror is often the only way to know whether another vehicle is there. A collision caused by not checking a side mirror can injure or kill someone, which is why every state requires them.
The angle of a side mirror is important. If it is angled too far inward, it shows mostly your own car door. If it is angled too far outward, it shows mostly empty road. The right angle shows the side of your car in a small portion of the mirror and the lane next to you in most of it.
Key Takeaways
- Side mirrors show the lanes beside your vehicle and reduce blind spots that your rearview mirror cannot cover.
- Most vehicles have adjustable side mirrors that you can move from inside the car using a control dial or joystick on the driver's door.
- The correct mirror angle shows a small sliver of your car's side and most of the lane next to you, not mostly your own vehicle or mostly empty road.
- If a side mirror is cracked, loose, or missing, it is unsafe to drive and should be repaired or replaced before you operate the vehicle.
- Convex (curved outward) mirrors show a wider view than flat mirrors but make objects appear farther away than they actually are.
How to adjust your side mirrors correctly
Most modern vehicles let you adjust side mirrors from inside the car using a control on the driver's door panel. This control is usually a small dial, joystick, or rocker switch labeled with arrows or a mirror symbol. You select which mirror you want to move (left, right, or both) and then use the arrows to tilt the mirror up, down, left, or right.
To set the correct angle, sit in the driver's seat and look at the left mirror first. Adjust it so that you can see a small strip of your car's side on the right edge of the mirror, and the lane next to you fills most of the mirror. Then do the same for the right mirror. When both mirrors are set this way, you eliminate most of the blind spot that exists between what your rearview mirror shows and what you can see by turning your head.
Some vehicles have power-folding mirrors that tuck in when you park, or heated mirrors that melt ice and snow. These features do not change how you adjust the angle — the same dial or joystick controls them. If your vehicle has manual mirrors (rare on newer cars), you adjust them by reaching out the window or opening the door and moving the mirror by hand.
Types of side mirrors and what they show
Most side mirrors are flat mirrors, which show objects at their actual distance. A flat mirror is the most accurate for judging how far away another vehicle is, which is why they are standard on the driver's side in most places.
The passenger-side mirror is often convex (curved outward), which means it shows a wider area than a flat mirror but makes objects appear farther away than they really are. A convex mirror reduces blind spots, but you have to remember that a car you see in it is closer than it looks. Some vehicles let you choose between flat and convex mirrors, or have a flat driver-side mirror and a convex passenger-side mirror.
Older vehicles sometimes have manual mirrors that you adjust by hand from outside the car. These are less common now but work the same way — you move them to the correct angle and leave them there. Manual mirrors are cheaper to replace if they break, but they cannot be adjusted from inside the car.
What to do if your side mirror is damaged or missing
A cracked, loose, or missing side mirror makes it unsafe to drive because you lose the view it provides. In most states, driving without a side mirror or with one that does not work is illegal, and you can be stopped by police. More importantly, you lose the ability to see a blind spot, which puts you and other drivers at risk.
If your mirror is cracked but still in place and moves, you can usually drive carefully to a repair shop, but do not delay. If the mirror is hanging loose, dangling, or missing entirely, do not drive the vehicle — have it towed or repaired before you operate it on a public road.
Replacing a side mirror can cost anywhere from under $100 to several hundred dollars depending on whether it is a straightforward manual mirror or one with power adjustment, heating, or integrated turn signals. Some repair shops can install an aftermarket mirror (a non-manufacturer part) for less than a dealer mirror. Check your insurance policy — some comprehensive plans cover mirror damage.
Why side mirrors have blind spots even when adjusted correctly
Even with side mirrors adjusted perfectly, a blind spot still exists — an area you cannot see in any mirror or by looking over your shoulder. This is why checking your side mirror is not enough when you change lanes. You also need to glance over your shoulder or use your vehicle's blind-spot warning system if it has one.
The blind spot exists because of the shape and size of your vehicle. Your car's body, roof, and rear pillars block the view from certain angles. A side mirror can show the lane next to you, but it cannot show the area directly beside your rear door or the corner behind your vehicle. That is why defensive drivers check the mirror, glance over their shoulder, and only then move into another lane.
Blind-spot warning systems and how they work
Many newer vehicles have blind-spot warning systems that use radar or cameras to detect vehicles in your blind spot. When a car enters the area you cannot see, a light appears on or near the side mirror, or an alert sounds. Some systems also prevent you from changing lanes if a vehicle is detected, or they gently steer you back into your lane if you start to move toward a car you did not see.
These systems are helpful, but they are not a replacement for checking your mirrors and looking over your shoulder. They can fail, miss motorcycles or small vehicles, or be fooled by road markings or guardrails. Treat them as an extra layer of safety, not as a reason to skip your own checks.
Frequently Asked Questions
Why does my passenger-side mirror show things farther away than they are?
Most passenger-side mirrors are convex (curved outward), which gives a wider field of view but makes objects appear more distant than they actually are. This is intentional — it reduces blind spots. The tradeoff is that you have to remember objects are closer than they look. Your driver-side mirror is usually flat for accurate distance judgment.
Can I drive without a side mirror if I have a backup camera?
No. A backup camera only shows what is behind you when you are in reverse. Side mirrors show what is beside you while you are driving forward, changing lanes, and merging. A backup camera does not replace a side mirror, and driving without one is illegal in most places.
What should I do if my side mirror keeps getting knocked out of position?
If your mirror is loose or moves too easily, the adjustment mechanism may be worn or damaged. Have it inspected at a repair shop — a loose mirror can fall off entirely while you are driving. If it is being hit by other vehicles or objects, park in a different location or have the mirror replaced if it is damaged.
Do I need to adjust my side mirrors every time I drive?
No. Once you set your side mirrors to the correct angle, they should stay there. You may need to readjust them if someone else drives your car, if you change the seat position significantly, or if the mirror gets bumped. Check them occasionally to make sure they have not shifted.
Is it better to have flat or convex side mirrors?
Flat mirrors on both sides give the most accurate view of distance but leave larger blind spots. Convex mirrors reduce blind spots but make objects look farther away. Most vehicles use a flat driver-side mirror for accuracy and a convex passenger-side mirror for wider coverage. Choose based on what helps you feel most confident and safe.