Mine for 5 chicks was pen about 4x4 and 2 1/2 feet high. That worked until we moved them out at 5 weeks. It could have gone a little longer but not too much. I don't think a typical plastic bin would last all the way through
The brooder was actually 4gates of a baby pen. I'll see if I can find a pic of it. I put up poster board on the lower half when they were tiny so they couldn't squeeze out. Then we had screens that went on top. The heat lamp suspended from a board that went across the top .
At 5 weeks a moved them out to the coop and run during the day (the first day or two just during the afternoon but then dawn to dark). Then moved them out to the coop and run full time at a few days short of 6 weeks. Here's their coop/run set up.
Straight sides of the run are 3 feet tall and then there is a domed roof (you can barely see it in the picture). For 5 chicks. the coop is 3x4 plus the nesting box. The run is 4x17. They seem happy.
If this is outside, with juveniles in it, it is a 3x8 grow out pen.
If I drag in inside the garage, it is a brooder.
But my favorite place to brood is in my 5x8 utility trailer. Lots of room, no rush. The only problem is committing the 5 weeks to it takes the trailer out of commission for that period. I particularly like the cleanout at the end. Take the trailer to the gardens and sweep it out, one time. Done.
6 chicks at 6 weeks are going to need a very minimum of 12 square feet, so that'll give you some idea what you're looking for. I brood in galvanized livestock troughs, but understand those aren't for everyone lol. My second go-to is large cardboard boxes. Get two of them, tape them together side by side and cut a door between them. This automatically gives you a warm area and a cool area and prevents the all-to-common problem of chicks becoming cooked nuggets from overheating. Heat lamp on one side, feed and water in the other box. Pine shaving on the bottom, plus when you're done it can all go in the garbage or the compost.
great info - thanks for the response. taking in all this for my own situation. brooder will have to be in my home (home office or formal dining room we never use (except for turkey day) ) so your experience doesn't apply but good info on size consideration for me to target and I like the idea of two zones - seen that in other online info. thanks again ! Sam