full suspension whole/frame only mountain bike box dimensions
Depends how broken down / disassembled it is.  Normally a new bike is shipped in a box with the front wheel removed or sometimes both wheels removed.



The front wheel is beside the bike.  The rear wheel is left in here, probably to stop the chainrings from carrying the weight.

Its not unusual to have the forks both protected and extended by packaging, again to keep the pressure off the more delicate parts, and to protect paintwork and disc caliper.

Saddle and post are often removed for height reasons even though the width there would be okay.

Bars and stem are normally completely disconnected, which can cause issues with pre-charged hydraulic brake lines.

Pedals always come off too.   All these small parts are stored around the bike, either between the chainring and the forks, or sometimes in packing and then cable-tied to the frame, which also wears packing.



So reading into your question, you feel like you're being overcharged on shipping for a bike?


Remember the shipment may be coming from another country.  Not uncommon in these days of globalisation.
Shipment cost may include


insurance
import duties
customs fees
cleaning/fumigation fees (yes sounds silly for a new item)

This may be how the super-cheap bike seller recoups some of their costs, by moving some of their markup onto the freight cost.



  You should re-evaluate the cost of buying from your Local Bike Shop, given they have paid for all the transport costs already.