WiFi Signal Strength Calculator

WiFi coverage problems are one of the most common IT complaints in homes and offices. Dead zones, slow speeds in conference rooms, devices dropping connection near windows — most of these are predictable and preventable with basic signal planning. The CalcHub WiFi Signal Calculator takes the guesswork out of access point placement.

Understanding Signal Strength: dBm Explained

WiFi signal is measured in dBm (decibels relative to 1 milliwatt). The scale is logarithmic and goes negative — higher (less negative) numbers mean stronger signal:

Signal (dBm)	Quality	What It Means
-30 dBm	Excellent	You're basically next to the AP
-50 dBm	Very Good	Fast, reliable connection
-60 dBm	Good	Normal usage works well
-70 dBm	Fair	Web browsing okay, streaming may buffer
-80 dBm	Poor	Basic connectivity only
-90 dBm	Unusable	Frequent disconnections

Most devices stop attempting connection around -90 dBm. A device showing 1 bar of WiFi is typically at -75 to -85 dBm.

Free Space Path Loss

In open air with no obstacles, signal degrades with distance following this formula:

FSPL (dB) = 20log₁₀(d) + 20log₁₀(f) + 20log₁₀(4π/c)

Where d = distance in meters, f = frequency in Hz. The calculator handles this math. Practical takeaways:

Frequency	Every time you double distance	Signal loss
2.4 GHz	Double distance	~6 dB loss
5 GHz	Double distance	~6 dB loss (but starts higher)
6 GHz (WiFi 6E)	Double distance	~6 dB loss (higher starting loss)

5 GHz has higher path loss than 2.4 GHz at the same distance, which is why 5 GHz coverage radius is smaller. But 5 GHz suffers less interference and supports wider channels, so it's faster where signal is adequate.

Material Attenuation (Signal Through Walls)

Material	Signal Loss (approx)
Drywall	3–5 dB
Concrete / brick	10–15 dB
Reinforced concrete	15–25 dB
Glass (standard)	2–3 dB
Metal / foil insulation	20–30 dB
Floor (wood)	10–15 dB
Elevator shaft / metal door	40+ dB

Enter your AP transmit power, frequency, distance, and number/type of walls in the calculator to get the expected received signal strength at any point.

Example: Office Coverage Planning

You have a 40m × 30m open-plan office on a single floor, concrete exterior walls, internal drywall partitions. AP transmit power: 20 dBm, antenna gain 4 dBi, 5 GHz.

Running a path loss estimate for 15m with 1 drywall partition:

• Free space loss at 15m, 5 GHz: ~56 dB


• Drywall: 4 dB


• Total loss: 60 dB


• Received signal: 20 + 4 - 60 = -36 dBm (excellent)

At 25m, 2 partitions:

• FSPL: ~62 dB, partitions: 8 dB, total: 70 dB


• Received: 20 + 4 - 70 = -46 dBm (very good)

One centrally-placed AP likely covers the whole floor at 5 GHz for most of the area. The corners at 35m with exterior concrete walls might dip to -70 dBm — the calculator flags these and suggests a second AP or a mesh node placement.

Tips

• Channel width matters. 80 MHz channels on 5 GHz offer higher throughput but more noise susceptibility. In dense environments with many APs, 40 MHz channels often give better real-world performance.
• 2.4 GHz has only 3 non-overlapping channels (1, 6, 11). Co-channel interference from neighbors on the same channel can be worse than the lower range of 5 GHz.
• Elevate your access point. Mounted near the ceiling, an AP has line-of-sight to more of the floor area. An AP sitting on a desk behind a monitor is a real waste of its coverage potential.

How many access points do I need for a 2,000 sq ft home?

One well-placed AP on each floor usually suffices for 5 GHz in most homes. In open-plan layouts, one central AP covers 2,000 sq ft comfortably. Add a second if there's a far end with thick walls.

Why is my 5 GHz connection faster but shorter range?

5 GHz operates at higher frequency, which means higher free-space path loss and more absorption by walls. The tradeoff is more spectrum, less interference, and wider channels. Most modern devices and routers handle band steering to connect at 5 GHz when close and fall back to 2.4 GHz when further away.

What is MU-MIMO and does it affect coverage?

MU-MIMO lets an AP serve multiple devices simultaneously instead of one at a time. It improves throughput in dense environments but doesn't extend coverage range. Coverage is still determined by path loss and signal strength.

Related Calculators

• Bandwidth Calculator — plan capacity alongside coverage
• Latency Calculator — WiFi latency vs wired comparison
• Network Uptime Calculator — reliability planning for wireless networks