6 mm or 8 mm Neon Tube, and How Small the Letters Can Go

Short answer: 6 mm tube is finer and allows smaller lettering, down to about 2 inches high. 8 mm tube is bolder and brighter, and needs letters of about 3 inches or more. Below the minimum, curves get too tight to bend, and the letters run together when lit.

These are the minimums Sign Designer uses. Your own supplier's tube may differ a little, so set yours to match.

Why there is a minimum at all

LED neon flex can only bend so tightly. A small letter, especially a lowercase "e", "a" or "s", has tight curves. If the curve is tighter than the tube allows, you either cannot make it, or it kinks.

Small letters also blur together. Lit tube glows wider than the tube itself, so the gaps inside letters, like the middle of an "e", fill with light and the word becomes hard to read.

6 mm tube

• Good: delicate script lettering, name signs, small desk signs and fine detail.
• Minimum letter height: about 2 inches.
• Feels: lighter and more elegant.

8 mm tube

• Good: bold words, larger wall signs and anything meant to be read from across a room.
• Minimum letter height: about 3 inches.
• Feels: brighter and chunkier.

Fonts that work as neon

Not every font makes a good neon sign. The fonts that work have:

• One line per stroke. Neon is a single tube, so a font drawn as an outline has to be turned into a center line first.
• Joined script, which can often be made with fewer pieces of tube and looks the most like traditional neon.
• Open shapes, with room inside the letters for the glow.

Fonts with very thin and thick strokes, or tiny details, rarely work.

Make it impossible to order the wrong size

The best fix is to stop the problem at the design stage. In Sign Designer:

• a Neon font filter shows only single-line and script fonts that bend well
• customers choose 6 mm or 8 mm tube, and each width has its own minimum letter height
• they see the sign glow at night before they submit

More on building the price in how to price LED neon signs.