Over 100ms most of the time, it worked fine for WFH when I had meetings. Terrible if you want to game.
This is interesting since I remember having much lower latency for 3G, perhaps < 50 ms, about 10 years ago. :) At that time, some of my friends were even using the home 3G to play games.
That's rare. T-Mobile averages 53ms latency according to Ookla/Speedtest.net for multi-server latency. For wired connections, Xfinity averages 24ms, Cox 25ms, and Spectrum 31ms. So wireless does add an additional ~25ms of latency compared to wired, but 100ms is out of the ordinary.
Try the fast.com or speed.cloudflare.com instead. Ookla is pretty easy to game by the ISPs
T-mobile != T-Mobile ISP. For the better or worse, anything going through the ISP plan is bottom of the barrel. You can look through all the post on the T-Mobile ISP subreddit. Even those with 500 Mbps speed are close to 100 ms of latency.
I've got Verizon 5G for $25/month extra on top of my cell phone bill, and the tower is right across the street. It's pretty competitive with Xfinity's 1.2Gbps service since they didn't bother throttling it. I also get 350Mbps up. Seeing 15ms pings to servers in Sacramento from SF.
Some of the people on my team had to switch back to Comcast after trying it for a few months. Video calls were laggy and would drop packets constantly. This was in Colorado fwiw.
Your experience is highly dependent on how close you are to the nearest mobile base station and its utilization profile. If it's distant or highly utilized, you will have degraded performance vs being closer or less utilized.