Best Car Magnet Sizes and Mil Thickness for Business Vehicles

Most people shopping for car magnets focus on the design and skip the two decisions that decide whether the magnet actually works: the size and the thickness. Get the size wrong and the magnet bridges a body line and never sits flat. Get the thickness wrong and it peels off on I-95. Here is how we help customers pick both at our shop in Westlake.

The Short Answer

• 12x18 inches for compact cars and smaller doors.
• 12x24 inches for most sedan and pickup doors. This is the size most people end up with.
• 18x24 inches for trucks, SUVs and vans with tall, flat door panels.
• 30 mil thickness if the vehicle ever sees highway speed.

Those are starting points, not rules. The only number that really matters is the flat area of your own door, so measure before you order.

Car Magnet Sizes: How to Pick the Right One

Step 1: Measure the Flat Area, Not the Whole Door

Grab a tape measure and look at the door from the side. You are looking for the largest flat rectangle that does not cross anything. Skip over:

• Body lines and creases. A magnet laid over a crease has an air gap on both sides of it, and air gaps are where wind gets in.
• Door handles and keyholes.
• Molding, trim strips and pinstripes. Anything raised keeps the magnet from making full contact.
• Curves near the wheel wells and the edges of the door.

Measure that flat area height and width, then pick the largest magnet that fits completely inside it with a little room to spare. If the magnet hangs over an edge or a line, go down a size. A smaller magnet sitting fully flat beats a bigger one that is lifting at a corner.

Step 2: Match the Size to the Vehicle

12x18 inches. Built for compact cars, small hatchbacks and doors where the flat area is short. It is also a good pick when a body line runs high on the door and cuts down the usable height.

12x24 inches. The everyday car door magnet size. It fits most sedan and pickup doors and gives you enough width for a logo, a service line and a phone number that can be read from the next lane.

18x24 inches. For trucks, SUVs and vans with tall flat doors or side panels. The extra height lets you run a bigger logo and larger phone number, which matters when people are reading it from across a parking lot.

Step 3: Think About What You Need to Say

A door magnet gets a few seconds of attention. On a 12x18, keep it to a logo, what you do, and a phone number or website. On an 18x24 you have room for a short list of services. If your layout is crowded on the size that fits your door, cut words before you go up a size.

30 Mil vs 20 Mil Car Magnets: Why Thickness Matters

Magnetic sign thickness is measured in mils. One mil is a thousandth of an inch. Our door magnets are 30 mil, which is about .76mm.

A lot of the cheap car magnets sold online are somewhere between 12 and 20 mil. They look fine on the listing photo. The difference shows up at speed.

What Thin Magnets Do

Thinner sheet is lighter and more flexible. At highway speed, wind gets under a corner, the corner lifts, more wind gets under it, and eventually the whole sign lets go. Thin magnets also tend to curl at the corners after a few weeks in the heat, which starts the same problem even when parked.

What 30 Mil Does Better

• Holds better at highway speed. Thicker sheet carries more magnetic material, so it grips the panel harder. Ours is rated at a minimum of 60 lbs of magnetic pull per square foot.
• Resists corner lift. The extra stiffness keeps the edges down instead of fluttering.
• Rounded corners. Square corners give the wind something to catch. Every magnet we print has rounded corners for that reason.

If the vehicle never leaves town, a thinner magnet might get by. If it ever sees the turnpike or I-95, 30 mil is the spec we recommend.

Make Sure Your Panels Are Steel

This catches more people than size or thickness. Magnets only stick to steel. They will not hold on aluminum, fiberglass or plastic panels. The Ford F-150 has used an aluminum body since 2015, and many Teslas use aluminum panels too.

The easy test: take a fridge magnet and put it on the exact spot where the sign will go. If it slides off or does not grab, a car magnet will not hold there either. Check both doors, since some vehicles mix materials.

Our Magnet Specs and Prices

Our 30 mil high-strength car magnets are full-color printed on 30 mil (.76mm) magnetic sheet with rounded corners, and they are rated from -15F to 160F. Most door magnets are ordered as a pair, one for each side of the vehicle.

• 12x18: $64 single, $84 pair
• 12x24: $68 single, $90 pair
• 18x24: $74 single, $104 pair

No artwork? We design it for $80, added at checkout. Turnaround is 3-5 business days, and we ship anywhere in the US. Local customers can call the shop at 561-323-7573.

Keeping Them On the Door

Size and thickness get you most of the way. The rest is how you treat the magnet: clean, dry, flat steel, and pulled off once a week so you can clean underneath. We cover all of that in Are Car Magnets Bad for Your Paint? Myths vs Facts.

Still deciding whether magnets are the right fit at all? Read Vehicle Magnets vs Vinyl Lettering vs Wraps, browse our decals and vehicle lettering, or see everything on our custom vehicle magnets page.

FAQ

What size car magnet do I need?

Measure the flat area of your door, avoiding body lines, handles and molding, and pick the largest size that fits inside it. As a guide, 12x18 fits compact cars, 12x24 fits most sedan and pickup doors, and 18x24 fits trucks, SUVs and vans.

What is the most common car door magnet size?

12x24 inches. It fits most sedan and pickup doors and has enough room for a logo, a short service line and a phone number.

Is a 30 mil car magnet better than a 20 mil magnet?

For highway driving, yes. 30 mil sheet holds the panel harder and resists corner lift. Many cheap online magnets are 12 to 20 mil, which are more likely to curl and peel off at speed.

Why won't my car magnet stick?

The panel is probably not steel. Magnets do not stick to aluminum, fiberglass or plastic. The Ford F-150 has had an aluminum body since 2015, and many Teslas use aluminum panels. Test the spot with a fridge magnet first.

Should I buy one magnet or a pair?

Most customers buy a pair so both sides of the vehicle carry the same sign. A pair costs less than two singles.

Measured your door and know your size? Order your door magnets online, or let us design them. Questions first? Call Arnold Prints at 561-323-7573, 17246 43rd Rd N, Westlake, FL 33470.