Before an adjective, demasiado means "too" and does not change: demasiado grande, demasiado caras. "Big enough" is grande o suficiente, with o suficiente after the adjective. In shops you will also hear muito used for "too": está muito apertado.
Examples
- Esta camisola é demasiado pequena.
- This jumper is too small.
- O casaco não é quente o suficiente.
- The coat isn't warm enough.
- Estas calças são demasiado compridas.
- These trousers are too long.
The mistake to avoid
Before an adjective demasiado never agrees: demasiado caras, never "demasiadas caras".
Where this fits in
Colours, clothes & likes, Portuguese A1: Name colours and clothes, buy something in the right size, and say what you like and don't like.