How can I tell how large my ship needs to be I am getting error "ship has no space to develop " I have click and use several points on the size of my ship but never seems to be large enough.

For the most part, your ship will never be big enough. You will have to equip and unequip things as needed.

And it says how much space is on your ship in the same place as it says your attack and defense. Its on the very top of that column.

Yes, It tells me how large my ship is but not how large it should be for each improvement. That is what I need to know now.

ok simple break down ship tab
Size Class: type of you ship
Space: ****size of ship say 40/45 means 40 used 5 avalible***
Attack: dmg you do
Defense: dmg reduction
Scan: scaning for ships and planets also caculats crits
Cloak: ablity to hide and spy
Cargo: room on ship for items not installed or cargo or artifacts.
so to tell the size of an item mouse over it or
1st. go into the tap i e wepon,defence/sheilds, hull etc...
2nd click on install new device button. and this chart comes up
Item Ability Cost Size Options

Heavy Mass Driver Attack +7 1,960 7 Build
Mass Driver Attack +5 1,400 6 Build
Light Mass Driver Attack +3 1,000 5 Build
in the situation above you would only be able to install the light mass driver because you have only 5 slots open....hope this helps and answeres your question.

Deck size is the "size" I believe you are looking for. However many decks you have determines how much you can equip on your ship. So if you have an energy module that has a size of 10, you will need to have 10 open deck spaces available. You can look under the ship tab and look on left hand side, it will tell you how much "Space" you have and how much you have available. IE - 76/81 means you have a total of 81 decks, but you are already using 76, therefore you have 5 available decks to use. So in the case of the energy module you would either need to uninstall something off the ship (something at least size of 5), or maybe level again and put all 5 rank points into decks. Then you would have the space to put in the module.

Side note - the Class Size (frigate/destroyer/etc), changes as your deck amount reaches certain points.