Type your legal business name and USDOT number, set the letter height in real inches, and download a true size PDF for the printer plus an SVG for the vinyl cutter. Free, no signup.
The federal marking rule for commercial motor vehicles is 49 CFR 390.21. What it actually requires is the legal name or a single trade name of the carrier, and the FMCSA identification number preceded by the letters USDOT. On the size question, here is what it comes down to. This is a plain English summary written by us, not the wording of the regulation itself:
The marking must appear on both sides of the vehicle, be in letters that contrast sharply in colour with the background, be readily legible during daylight hours from a distance of 50 feet while the vehicle is stationary, and be kept and maintained so it stays legible.
There is no 2 inch federal minimum. Two inch lettering is simply the size the sign trade settled on because it clears the 50 foot test comfortably, which is why this page starts there. Read the rule yourself at eCFR, 49 CFR 390.21.
Your state may be stricter. Several states set their own minimum letter heights for intrastate carriers, and trades such as towing and passenger transport carry extra requirements. Check your state rules, and if you run under another carrier's authority you may also need an "Operated by" line. This page is a layout tool, not legal advice.
Use the name exactly as it appears on your MCS-150, or a single registered trade name.
Panel
This is cap height, the height of a capital letter, which is what a sign shop means by letter height. It is measured back off the drawn outline, not guessed from a point size.
Squeeze the letters horizontally to fit a long name without giving up letter height.
Colour
Turn the background off for cut vinyl that goes straight onto the paint. The contrast check then runs against the vehicle colour instead.
Output
Both door panels are identical. Nothing is mirrored unless you tick the reverse box, which is only for film applied to the inside of a window.
Colours here are RGB. A printer converts to CMYK and the shade can shift a little, so ask for a proof if it has to match a brand colour exactly. Nothing you type is uploaded and there is no file to upload: the layout is drawn in your browser. The page does pull two code libraries and one font file from public CDNs.
Almost every free design tool asks for a font size in points and leaves you to guess what that becomes on a door. Points are not inches, and a point size is not a letter height either, because a capital letter only fills part of its em. In a typical sans face, 144 point type gives roughly 1.4 inches of capital, not 2, which is exactly how carriers end up with lettering smaller than they thought they ordered. This page works the other way round. You give it the letter height you want in inches, it solves for the type size that actually measures that, then it re measures the drawn outline to confirm. The number on the stats row is the real height of a capital letter on the finished panel.
A PDF at true size. Each panel is its own page at the exact cut size plus the bleed you chose, and crop marks sit in the bleed whenever you leave a bleed on. The lettering is converted to vector outlines before it is written, so there is no font to go missing and no chance a shop's print software substitutes something else. If the outline font cannot be downloaded, the page says so on screen and falls back to live text, which a shop renders with its own font. Zoom in as far as you like, the edges stay sharp.
An SVG for the cutter. The same layout as real glyph outlines, sized in inches, with the panel perimeter on its own layer as a cut path. Drop it into your cutter software, or send it to a shop that asks for vector art. In that same fallback case it carries live text instead, and the file's own description says so.
A PNG preview. The panel shown on a flat van, pickup or box truck at true relative size, so you can see whether it suits the door before you pay for it. A panel bigger than the door area is shrunk down to fit the picture rather than drawn overhanging, and when that happens both the image and the warning box say so.
Federal rules do not name a material. Magnetic panels are widely used and are legal as long as the marking meets the legibility requirement and is maintained, and plenty of carriers run permanent cut vinyl instead. Some states, insurers and shippers have their own preferences, so check before you commit to magnets on a long term vehicle. If you do order magnets, buy the 30 mil grade for highway speeds and take them off now and then so moisture does not sit against the paint.
It does not check that a USDOT number exists, is active, or belongs to you. It does not know your state's rules. It does not know whether you need an "Operated by" line because you run under another carrier's authority. It produces artwork, and the responsibility for what the artwork says stays with you. If your operation is unusual, a five minute call to your state motor carrier office is cheaper than a roadside violation.
Sign shops normally bill an art and layout fee of roughly one hundred to two hundred and fifty dollars per vehicle before anything is printed, and pre made USDOT number decal sets run twenty five to forty five dollars a pair for two lines of type. A correct, true size PDF is what a shop needs to skip the layout step, so many will drop or reduce the art fee for it, though that is the shop's call and some charge a file check instead. Either way it leaves you holding a file you can send to any printer, instead of the one who owns your artwork.