How to Fix WiFi Interference From Cordless Phones: Channels, DECT, and Band Fixes

Your WiFi was fine until you plugged in that new cordless phone — now speeds dip during calls and devices drop off the network. Cordless phones are one of the most overlooked sources of wireless interference, yet the fix is almost always simple once you understand which frequencies are at fault.

Why Cordless Phones Interfere With WiFi

WiFi and certain cordless phones share the same radio spectrum. When two devices broadcast on overlapping frequencies near each other, their signals collide and corrupt data packets. Your router and devices have to retransmit those packets, which shows up as slower speeds, higher latency, and occasional drops.

The severity depends entirely on which frequency your cordless phone uses.

2.4 GHz Cordless Phones — The Main Culprit

Older cordless phones labeled “2.4 GHz” (non-DECT models sold before roughly 2010) transmit directly in the 2.4 GHz ISM band — the exact same spectrum used by WiFi 802.11b/g/n/ax. These phones can blast enough power to completely kill WiFi within several feet and noticeably degrade it across a room. If you have one of these, it is the most likely cause of your problem.

5.8 GHz Cordless Phones

Phones marketed as “5.8 GHz” transmit in the 5.725–5.850 GHz range. That band sits at the upper edge of WiFi’s 5 GHz channels (U-NII-3, roughly 5.745–5.825 GHz). Interference is less common than with 2.4 GHz phones but can still affect WiFi channels 149–165. Moving your router to a lower 5 GHz channel (36–48) eliminates the overlap entirely.

DECT 6.0 Phones — Safe to Use

DECT 6.0 is the modern standard for cordless phones sold in the US. Despite the “6.0” in the name (a marketing designation, not a frequency), DECT 6.0 phones operate at 1.9 GHz — a band entirely separate from WiFi. They cause zero interference with any WiFi band: 2.4 GHz, 5 GHz, or 6 GHz. If your phone says “DECT 6.0” on the box, it is not your problem.

How to Tell If Your Phone Is Causing Interference

Run a WiFi speed test while no one is on the phone and note the result.
Have someone make or receive a call on the cordless phone, then run the speed test again immediately.
If speeds drop significantly or devices disconnect during the call, the phone is the source.
As a secondary check: unplug the phone base from the wall entirely and see if your WiFi stability improves over the next hour.

You can also use a WiFi analyzer app (like WiFi Analyzer on Android or the built-in Wireless Diagnostics on macOS) to watch your signal-to-noise ratio in real time during a call. A sudden rise in noise floor confirms the interference. See our guide to using a WiFi analyzer for step-by-step instructions.

Fixes: Stop Cordless Phone WiFi Interference

Fix 1: Upgrade to a DECT 6.0 Phone

This is the permanent solution. Any phone with “DECT 6.0” on the label operates at 1.9 GHz and is completely safe to place next to your router. Major brands like VTech, Panasonic, and AT&T all sell DECT 6.0 systems for under $40. This single upgrade eliminates the interference problem entirely.

Fix 2: Move Your WiFi to 5 GHz (and Force Devices Off 2.4 GHz)

Even with a legacy 2.4 GHz cordless phone in the house, your performance problems disappear if your devices connect via 5 GHz. Log into your router admin panel and either disable the 2.4 GHz radio entirely (practical if all your devices support 5 GHz) or create a separate 5 GHz SSID and connect your speed-sensitive devices to it. See our guide on how to connect to the 5 GHz band for device-by-device instructions.

Fix 3: Change Your 2.4 GHz WiFi Channel

If you must keep the 2.4 GHz radio on, switch to a channel that overlaps least with the phone’s transmission. In the US, the 2.4 GHz band has 11 channels, but only three are non-overlapping: channels 1, 6, and 11. Many 2.4 GHz cordless phones concentrate their interference around channel 6. Try channel 1 or channel 11 first. Log into your router (typically at 192.168.1.1 or 192.168.0.1), go to the Wireless or WiFi settings section, and set the channel manually rather than leaving it on “Auto.” Our full walkthrough on how to change your WiFi channel covers this for all major router brands.

Fix 4: Physically Separate the Phone Base From the Router

RF interference drops off rapidly with distance. Moving the cordless phone base at least 10 feet (3 m) from your router reduces interference significantly even without changing any settings. Never place a 2.4 GHz phone base on top of or directly beside your router.

Fix 5: Update Router Firmware

Some older router firmware has less aggressive interference mitigation. Check your router manufacturer’s website or admin panel for firmware updates. Modern firmware versions include improved dynamic frequency selection (DFS) and better noise-floor handling. Our guide on updating router firmware walks through the process for the most common brands.

Quick Reference: Cordless Phone Frequencies and WiFi Safety

900 MHz phones: Safe — no overlap with any WiFi band
1.9 GHz / DECT 6.0 phones: Safe — operates between cellular and WiFi bands
2.4 GHz phones (non-DECT): Dangerous — direct conflict with 2.4 GHz WiFi; replace immediately
5.8 GHz phones: Moderate risk — can affect high-numbered 5 GHz WiFi channels; move router to channels 36–48

Summary Checklist

Check the phone label: DECT 6.0 = safe; 2.4 GHz = replace
Run a speed test during a call to confirm interference
Upgrade to any DECT 6.0 handset for a permanent fix
Force speed-sensitive devices to 5 GHz or 6 GHz
Manually set your 2.4 GHz WiFi to channel 1 or 11
Keep the phone base at least 10 feet from the router
Update router firmware for improved noise handling

Cordless phone interference is one of the easiest home network problems to solve — a $35 DECT 6.0 replacement phone or a quick channel change in your router settings is usually all it takes. Once you’ve eliminated the phone as a variable, run another speed test to confirm your baseline has improved.