How small can I go....??

This summer I want to put in a small round pen to kinda work on the horses w/ ground manners etc.,just somewhere that's got safe ground but doesnt take up alot of room.We are using about every inch we have for the horses paddocks, so very limited and can't do it in existing (very) small field due to drainfield.But we have another small area that will be another turnout area for them so I was going to use part of that for a round pen w/ those panels things.Any help would be great.

I wouldnt go smaller than 10m diameter.

It really depends on what you are planning to do in the roundpen. If you plan to do a lot of lunging, then it needs to be bigger. If you are just planning on using it for close work like flexing and bending and respect, then I think that about 20 feet would be big enough but that is not quite big enough for extended lunging lessons.

For ground manners, starting colts, just basic work I like 40 foot dia. If your going to do anything with cattle I like 80 feet.

I like a 45' for off the back training but 60' for ridding (nothing faster then a slow jog).

No cows,no babies just a couple dumb geldings. I would love room to lunge but doubt I could make one big enough.Thanks for the input.They usually get enough exercise trail riding but for those winter days I'd like a place to work w/ them.

25m is the smallest I like to work with, anything smaller is pretty much useless.

I think we are going to build it ourselves, way cheaper...and we will go at least 40', and any space I have to mess w/ my horses that has safe ground etc wont be useless.Besides the horses paddocks etc., we have cement everywhere so you can see why we need a 'space' to work w/ them.