How to Convert Sign Sizes: Inches to Centimeters

If you are ordering a storefront sign from a US or Canadian supplier, you will see sizes in inches, while most factory drawings and international freight documents use centimeters. The inches to centimeters conversion is simple: multiply the inch measurement by 2.54. Use the rule carefully, because one wrong conversion can affect the whole sign layout.

By EndPoint Sign · Factory-direct signage, Guangzhou

1. How to convert inches to centimeters for sign sizes

A 24-inch channel letter is 60.96 cm tall. A 12-inch letter is 30.48 cm. You do not need a long formula or a calculator with special buttons; you multiply by 2.54 and round to one decimal place for a quote, or to the nearest millimetre when a drawing must be exact.

This matters because the same sign is described differently at each stage. A customer measures the wall in inches. A US permit reviewer may want feet and inches. A production drawing is often written in millimetres or centimetres. If any one of those numbers is converted incorrectly, the sign can arrive too large for the wall, too small to read from the street, or with letters that no longer match the approved artwork.

2. Common sign size conversion chart

Use this chart for the sizes business owners ask about most. The centimetre values are rounded to one decimal place, which is enough for a quote and for a first wall check.

If you already know you want a 24-inch sign, see our dedicated 24-inch channel letters guide for how that height is measured and what it costs.

For a quick mental check, remember three anchors: 10 inches is 25.4 cm, 20 inches is 50.8 cm, and 30 inches is 76.2 cm. If you think in feet, one foot is 30.48 cm, so a 6-foot sign is 182.88 cm.

3. What "24 inch" actually measures

The most common sizing mistake is assuming the inch number describes the whole panel. It does not. For channel letters, the quoted height usually refers to the capital letter height, or cap height, of the main letters. The backing panel, raceway, trim, or mounting hardware can add more space around it.

Lowercase letters and descenders also change the visual size. A word with a tall "H" and a lowercase "g" needs more vertical room than a word in all capitals. If the sign must fit between a window and an awning, measure that gap first and tell the factory the maximum overall height, not just the letter height.

4. How to measure your wall correctly

• Measure the available width and height in inches, at the exact place the sign will sit.
• Measure the letter area separately from the panel or raceway area, so the factory knows both.
• Check the clearance around doors, windows, vents, and conduits — these objects usually set the true maximum size.
• Take a straight-on photo with a tape measure in the frame — this removes guesswork when we create the 1:1 drawing.

Send the measurements in inches if that is how you measured them. We convert to centimetres and millimetres on the production side, so you do not need to do the math twice.

5. Real example: a spa sign measured to the fraction of an inch

One of our spa projects in Michigan is a good example of why exact conversion matters. The storefront had an existing junction box that left only 8 inches of vertical clearance above the door. We worked through two options with the owner: reduce the letter height to 6 inches, or relocate the electrical box upward.

The owner and her electrician moved the box, which allowed a 13-inch backer panel with 8.43-inch letters. In centimetres, that is a 33 cm backer with 21.4 cm letters. The difference between "about 8 inches" and "8.43 inches" is small on paper, but it was the difference between the sign fitting cleanly above the door and being blocked by the hardware. You can read the full measurement process in our spa sign case study.

6. Why permits and quotes use different units

Municipal permit forms in the United States often ask for dimensions in feet and inches, while the factory drawing may show millimetres. That is normal. Keep one master measurement and convert from it, rather than remeasuring in each unit. We supply imperial dimension sheets and electrical schematics for permit applications, so the numbers on your application match the numbers on the drawing. For general readability guidance, the International Sign Association is the reference body we follow.

For pricing, the unit conversion rarely changes the quote by itself. What changes the quote is whether the sign is 18 inches or 30 inches, because material, LED count, and crating all scale with the real physical size. That is why we ask for the finished dimensions before quoting a price. See our factory-direct price guide for how size moves the total.

7. Mistakes to avoid

• Measuring the old sign instead of the wall — the old sign may have been oversized or undersized for the space.
• Confusing overall size with letter size — a 24-inch letter on a raceway can need a 30-inch overall panel.
• Rounding too early — keep two decimals while converting, then round the final drawing once.
• Using a low-angle photo with no reference — a tape measure in the photo gives us a scale we can trust.
• Forgetting the clearance above a door — this is the most common reason a sign has to be redrawn.

8. How to send us the right numbers

You only need to send three things to start: the maximum width and height available, the preferred letter height in inches, and a straight-on photo with a tape measure if you can. We turn those into a 1:1 CAD drawing in either inches or centimetres, whichever your permit or installer prefers.

If you are not sure whether to measure in inches or centimetres, measure in the unit you are most comfortable with. Our engineering team handles the inches to centimeters conversion on the drawing, and we confirm the converted numbers with you before production starts.

Frequently asked questions

How do I convert inches to centimeters?

Multiply the number of inches by 2.54. For example, 24 inches × 2.54 = 60.96 cm.

Is a 24-inch sign measured as the panel or the letters?

For channel letters, the quoted height is usually the cap height of the main letters. The panel, trim, and mounting hardware add extra space around it.

What is 12 inches in centimeters?

12 inches is 30.48 cm, or about 30.5 cm when rounded for a quote.

Do I need to send measurements in centimeters?

No. Send the measurements in the unit you measured in, and we convert them accurately on the drawing.

Why does the sign factory ask for the wall clearance?

Because doors, windows, vents, and conduits set the true maximum sign size. A letter that looks correct on paper may not fit the physical gap above the door.

What if my permit form uses feet and inches?

That is fine. We provide dimension sheets in the units your municipality needs, converted from the same master measurement.