How to Estimate WiFi Coverage Without Expensive Site Survey Tools

Professional site survey tools like Ekahau cost thousands of dollars. For many projects, that's not in the budget. But you can still make informed decisions about AP placement using basic principles and free tools.

Understanding Signal Propagation

WiFi signals weaken with distance and obstacles. In free space, signal strength drops by 6 dB every time you double the distance. But you're not in free space—you're in a building with walls, furniture, and people.

Typical Wall Attenuation

Material	2.4 GHz Loss	5 GHz Loss
Drywall	3-4 dB	4-6 dB
Glass (standard)	2-3 dB	3-4 dB
Concrete block	10-15 dB	15-20 dB
Brick	8-12 dB	12-18 dB
Metal door	15-20 dB	20-25 dB

WiFi Coverage Calculator Estimate AP count based on area and environment type

The Rule of Thumb Approach

For typical office environments with drywall construction:

• 2.4 GHz: 40-50 feet (12-15m) radius through 1-2 walls
• 5 GHz: 25-35 feet (8-10m) radius through 1 wall

These are conservative estimates for usable coverage, not maximum range. You want overlapping coverage, not edge-of-signal areas.

Free Survey Methods

The Walk Test

If you have access to the space and one AP, set it up temporarily and walk around with a phone running a WiFi analyzer app. Note where signal strength drops below -70 dBm—that's your usable coverage boundary for most applications.

Floor Plan Estimation

1. Get or draw a floor plan to scale
2. Identify wall types and materials
3. Draw circles representing coverage radius (adjust for wall losses)
4. Place APs so circles overlap by 15-20%
5. Ensure no area is more than one wall away from an AP

High-Density Considerations

Coverage isn't just about signal reach—it's about capacity. An AP might cover a conference room, but can it handle 30 people with laptops and phones? For high-density areas:

• Plan for 25-30 clients per AP maximum
• Use more APs at lower power rather than fewer at high power
• Consider 5 GHz only for density (2.4 GHz has limited channels)

Channel Planning

Even with perfect placement, overlapping channels cause problems. On 2.4 GHz, only channels 1, 6, and 11 don't overlap in North America. On 5 GHz, you have more options but should still plan to avoid co-channel interference.

When You Need a Real Survey

These estimation methods work for simple spaces. Consider a professional survey when:

• The space has unusual construction (metal, concrete, glass)
• You need to support critical applications (VoIP, video)
• Client density is high (auditoriums, stadiums)
• The space is large or has complex geometry

A proper survey is cheaper than troubleshooting a poorly designed deployment after installation.