Boat Registration Number Requirements: Size, Spacing and Placement (33 CFR 173.27)

Compliance reference · Last verified 19 September 2026

Every state registers boats a little differently, but the way the number is displayed on the hull comes from one federal rule. Here it is, quoted, with the link.

What the regulation actually says

From 33 CFR 173.27 on the eCFR, quoted verbatim.

(a) Each number required by § 173.15 must

(1) Be painted on or permanently attached to each side of the forward half of the vessel except as allowed by paragraph (b) or required by paragraph (c) of this section;

(2) Be in plain vertical block characters of not less than 3 inches in height;

(3) Contrast with the color of the background and be distinctly visible and legible;

(4) Have spaces or hyphens that are equal to the width of a letter other than “I” or a number other than “1” between the letter and number groupings; and

(5) Read from left to right.

(c) Boats where the hull won't show it

On vessels so configured that a number on the hull or superstructure would not be easily visible, the number must be painted on or attached to a backing plate that is attached to the forward half of the vessel so that the number is visible from each side of the vessel.

Where people get it wrong

• Fonts. “Plain vertical block” rules out italic, script, outline-only and most slanted sport fonts. A number can be 4 inches tall and still fail if it leans.
• Spacing. The gap between the state letters, the numbers and the suffix has to be a full character wide. A thin gap, or none at all, is the most common miss we see on older boats.
• Contrast. Silver numbers on a white hull, or black on dark blue, can technically be 3 inches tall and still not be “distinctly visible and legible.” Add an outline or pick a contrasting color.
• Location. Forward half means forward of the middle of the boat. Numbers on the transom don't count.
• Starboard side. The number reads left to right on both sides. Don't mirror it for the right-hand side.

What it looks like

A Washington boat, for example, carries a number in the format WN 1234 AB: the state letters, a space, the numbers, a space, the suffix letters. Other states use their own two-letter prefix. Copy the number exactly as it appears on your registration card, letter for letter.

Why we cut 3 inches and up

Three inches is the legal floor. On a bigger hull, or one that sits high in the water, a slightly taller number reads better across the water and looks right for the boat. When you build a set we lay it out to scale and send you a proof, so you can see the size and spacing before anything is cut.

Nothing is cut until you approve your proof.

In Spokane or Coeur d'Alene? See boat registration numbers installed locally. Want to put them on yourself? Read how to apply vinyl numbers without bubbles.

Sources

• 33 CFR 173.27 — Numbers: display; size; color (eCFR)

Last verified 19 September 2026 against the current eCFR text. Your state's rules on validation decals and registration are separate. Check with your state boating agency.

JZAC Designs describes the standards we build to. We are a vinyl shop, not a compliance consultancy, and we do not advise on anyone's own regulatory obligations. Confirm final requirements for your situation with the agency that regulates it.