Safe distance needed to stop after 30m sprint?

Does anyone know what distance required to stop after a 10m, 20m or 30m sprint would be? I am thinking about buying some mats for training indoors.

depends on how fast you can go…!!

In my home town, there’s this small sports hall where I train sometimes. There’s a 50 meter track and I’m able to run 30 meters without hitting the wall at the end of the track.