There is no single number
The short answer is: it depends on the router’s hardware, not on your connection. A 1 Gbps fibre line with a mediocre router saturates sooner than a 100 Mbps fibre line with a good device.
What runs out isn’t bandwidth, but three internal resources: memory, the connection forwarding table and CPU time. That’s why dropouts appear long before the bandwidth is exhausted.
Real limits by device type
| Device | Practical limit | Symptom when exceeded |
|---|---|---|
| Basic ISP router | 10-15 devices | Random dropouts |
| Mid-range consumer router | 20-30 devices | High latency |
| Mid-range router | 40-60 devices | Acceptable stability |
| High-end router | 80-150 devices | High stability |
| Router with OpenWrt | 100-300 devices | Depends on the firmware |
ISP routers tend to sit at the bottom of the table. They usually run low-end processors, have very little memory and ship with closed-source firmware that reserves resources for features you’ll never use, such as the television service or the phone line.
The invisible limit: the connection table
Every connected device opens several simultaneous TCP and UDP connections. A video stream can involve a dozen of them, and with a smart TV, consoles and several phones the total adds up fast.
Every address handed out over DHCP also carries its lease with it, so the number of clients and the number of entries are not the same thing: RFC 2131 defines it.
If the router runs out of entries in the NAT table, it starts dropping packets. The symptom is random disconnections and pages that only half load, even though the signal is perfect.
Check: if the device shows the number of active connections, look at it with everything switched on.
Why the degradation is progressive
The router doesn’t break all at once. Typical degradation follows this script:
- It’s fine with 15 devices.
- Dropouts begin at 25, mainly in the browser and in streaming.
- It cuts out daily at 35, and the symptom looks like a signal problem even though it isn’t.
- It reboots on its own at 40 or more, when memory fills up and the watchdog process restarts it.
If you’re at step 2 and you’re looking for new antennas, you’re wasting time: the problem is inside the router.
The devices that load it the most
| Type | Load on the router | Comment |
|---|---|---|
| IP cameras | Very high | Several connections per camera |
| Smart TVs and consoles | High | Continuous streaming |
| Laptops and phones | Medium | Many short connections |
| Smart speakers | Medium | Lots of small conversations |
| ESP32 boards and sensors | Low in number | Little load, but very sensitive to dropouts |
| Smart lights | Low | Rarely the problem |
IoT devices are, paradoxically, the ones that generate the least load. If your network goes down and you have lots of smart home devices, the culprit is almost certainly not them but the rest of the equipment.
Symptoms of saturation
To tell them apart from a signal problem, check whether the dropouts affect everyone or only some devices:
| Symptom | Saturation? | Signal problem |
|---|---|---|
| Everything cuts out at once | Yes | No |
| Only in one room | No | Yes |
| Depends on the number of devices | Yes | No |
| Improves once you switch a few off | Yes | No |
| The router reboots on its own | Yes | No |
Ghost devices
Before buying anything, check you don’t have clients that don’t exist. A ghost device is one the router has assigned an IP to but that has been disconnected for weeks. It doesn’t load much, but it holds a DHCP lease.
You can spot them in the router’s lease table: if you see familiar IPs that don’t correspond to anything in your home, delete them. Every router has an option to release leases or restart the DHCP service.
How to expand capacity
If you’ve hit the limit, the options range from least to most invasive:
- Release ghost leases and reboot the router. Free.
- Update the firmware. Some older firmwares waste memory.
- Guest network for visitors, separating their traffic from your stable devices.
- Replace the router with one that has more resources. Start with replacing your ISP router.
- Split the network into several subnets with your own router and several access points.
If your problem is coverage as well as capacity, the route is a mesh system, which also spreads the load because each node handles its own clients.
Quick checklist
- You counted the devices that are really connected.
- You reviewed the DHCP leases looking for ghost devices.
- You checked the firmware version.
- You identified whether the dropouts affect everyone or just one room.
- You looked at the number of active connections if the router shows it.
- You only change equipment once capacity is confirmed as the problem.
Sources and next step
If the dropouts point to a signal problem rather than a capacity one, measure first with how to measure your home WiFi signal. And if the dropouts only affect smart home devices, the diagnosis is a different one: IoT devices disconnecting from WiFi.