New service panel ( old circuits too short)

[Trouyano]

Replacing old service panel, old circuit wires to short...
Need to add junction boxes. Can you put all circuits in one junction box (following box fill requirements) or is the max two per box with a two pole breaker for each pair. Thank you

 

[augie47]

As long as you follow the appropriate NEC rules, you can place as many as you wish in a j box.
There is no need for two pole breakers (or handle ties) on individual two wire 120 volt branch circuits unless you share neutrals.

 

[iwire]

Can you put all circuits in one junction box (following box fill requirements)

You can as Gus said but I suggest you go big. The NEC minumum box sizes are kind of tight in my opinion.

 

[stickboy1375]

As others have mentioned, go big... you wont regret it.