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LED Sign Sizing Guide — How to Choose the Right Sign for Your Window
Posted byBuying the wrong size sign is the most common mistake in LED sign procurement. Too small and it’s invisible from the street. Too large and it blocks your window, looks unprofessional, and may not fit the mounting position you had in mind.
This guide gives you the actual decision framework: window measurements, recommended sign sizes, minimum clearances, and visibility distances by sign size.
Step 1: Measure Your Window
Before you look at any product, measure your window. You need:
- Window width (inside frame to inside frame, in inches)
- Window height (inside frame to inside frame, or to the height where you want the sign’s lower edge)
- Clearance from window edge to obstacles — HVAC vents, light fixtures, door hardware, decorative elements that might block mounting
These three numbers determine which sign formats are viable for your window.
Window Width → Recommended Sign Width
| Window Width (inside frame) | Recommended Sign Width | Suggested Model |
|---|---|---|
| Under 24 inches | 10-12 inches | 10×24 or 10×27 format |
| 24-36 inches | 12-18 inches | 10×27 or 15×32 format |
| 36-60 inches | 18-24 inches | 15×32 format (standard) |
| 60-90 inches | 20-30 inches | 15×32 or 19×38 format |
| 90 inches or wider | 24-36 inches | 19×38 or larger; consider two signs for wide windows |
The 25-35% rule: your sign’s width should fill roughly 25-35% of your window’s width. Below 25%, the sign is too small to register clearly from the street. Above 35%, the sign starts to dominate the window and block sightlines into your space.
Standard Sign Formats and Their Best Applications
10×24 and 10×27-inch signs
Appropriate for:
- Narrow urban storefronts (24-36 inch windows)
- Secondary windows and supplemental sign positions
- Interior signage (reception desks, check-in windows, service counters)
- Businesses where the primary window already has a larger sign
Visibility: readable from 75-100 feet in standard ambient light. Sufficient for pedestrian traffic and slow-moving vehicles in dense urban contexts.
15×32-inch signs (the commercial standard)
Appropriate for:
- Most restaurant, retail, salon, and service business storefronts
- Standard commercial strip-mall units (typically 40-72 inch window widths)
- Primary window placement
- The majority of commercial storefront applications
Visibility: readable from 100-150 feet in standard ambient light, 200+ feet at night with a clear sightline. This is the format that covers most use cases.
GLI1050B and GLI1057B are both available in this format.
19×38-inch and larger signs
Appropriate for:
- Large plate-glass storefronts (typically found in newer construction)
- Corner locations with multiple window exposures
- High-speed vehicle traffic environments (40+ mph arterial roads, highway-adjacent commercial)
- Any location where extended visibility distance is a priority
Visibility: readable from 175-225 feet in standard ambient light. At 40 mph, this gives a driver approximately 3-4 seconds of visibility — enough to register the sign and make a lane change to turn in.
Visibility Distance by Sign Size
These are practical estimates for standard commercial LED signs in typical ambient light conditions. Actual visibility varies with sign brightness (nit rating), background contrast, and the viewer’s angle of approach.
| Sign Format | Daytime Visibility (typical) | Night Visibility (typical) |
|---|---|---|
| 10×24 / 10×27 | 75-100 feet | 150-175 feet |
| 15×32 | 100-150 feet | 175-225 feet |
| 19×38 | 150-200 feet | 225-300 feet |
| 24×48+ | 200+ feet | 300+ feet |
High-nit models (like the GLI1057B) extend daytime visibility by approximately 20-30% compared to standard-brightness models of the same size. The improvement is most significant in high-ambient-light conditions (bright afternoon sun, south-facing windows).
Mounting Clearance Requirements
Before finalizing your sign position, check these clearances:
Suction cup mount (glass):
- Minimum: flat, clean glass surface at least 4 inches wider on all sides than the sign face
- Avoid: textured glass, frosted glass, glass with applied films or tints (suction adherence is reduced)
- Height clearance: sign should be positioned at least 3 inches from any window frame, corner bead, or trim element
Chain hang from ceiling mount:
- Chain length: most signs ship with 24-36 inch chains. Add extension chain if ceiling height requires
- Anchor point: eyehook or ceiling bracket rated for at least 10 lbs (most LED open signs weigh 2-5 lbs — this is safety margin)
- Horizontal position: 6-12 inches from the window glass to avoid interference with window operation
Screw mount to wall or backer board:
- Use appropriate wall anchor for your wall type (drywall anchor for non-stud positions, lag bolt into stud)
- Minimum clearance: 2 inches between sign back and wall surface for heat dissipation (some signs run slightly warm at the power supply)
- For outdoor mounting: signs must be rated for outdoor use (IP65 or higher). Standard GLI open signs are indoor-rated unless otherwise specified.
Power Requirements
All standard GLI LED open signs operate on 110-120V AC, standard U.S. outlet voltage. No special wiring or dedicated circuit required.
Power consumption by sign format:
| Sign Format | Typical Power Draw |
|---|---|
| 10×24 / 10×27 | 8-12 watts |
| 15×32 | 12-18 watts |
| 19×38 | 18-25 watts |
For reference: 18 watts is less than a single 20-watt LED bulb. You will not notice this on your electricity bill.
Cord length: most signs ship with a 6-foot power cord. If your outlet is further away, use a quality heavy-gauge extension cord (16-gauge or better for cords up to 25 feet). Avoid daisy-chaining extension cords.
Special Situations
Corner locations: if your storefront has two window faces at a corner, run a sign on each face. The goal is a sign visible to traffic approaching from each direction. Use the same size sign on both faces for visual consistency.
Second-story windows: second-story placement is not recommended for open signs. Drivers and pedestrians read signage at first-floor eye level. A second-floor sign is typically not effective at driving foot traffic.
Narrow transom windows: transom windows (the narrow horizontal windows above a door or another window) are usually too narrow for a standard LED sign. A 10×24-inch format may fit, but measure first — transom windows often have less clearance than they appear.
Indoor positioning: some businesses position their open sign slightly inside the window (behind the glass) rather than directly on the glass. This is fine for clarity and sign protection, but adds distance between the LED panel and the viewer’s sightline. Compensate by using the sign format one size up from what the window-width chart recommends.
Quick-Reference: Sign Size by Business Type
| Business Type | Common Window Size | Recommended Sign |
|---|---|---|
| Restaurant, bar, cafe | 40-72 inch window | 15×32 (GLI1050B or 1057B) |
| Nail salon, hair salon | 24-48 inch window | 10×27 or 15×32 |
| Dispensary | 36-60 inch window | 15×32 (check state color rules) |
| Convenience store | 48-72 inch window | 15×32 or 19×38 |
| Boutique retail | 36-60 inch window | 15×32 |
| Gym / fitness studio | 48-96 inch window | 15×32 or 19×38 |
| Government / office lobby | Varies | 15×32 or custom; contact us |
Shop LED Open Signs → Read the Install Guide → Contact Us for Custom Sizing Questions →
*Green Light Innovations has designed and sold LED business signs since 2008. U.S.-based service.



